Wireless communication apparatus and method for generating midamble and controlling transmission power

ABSTRACT

The present technology relates to a wireless communication apparatus and method by which communication can be performed with a higher efficiency. 
     The wireless communication apparatus includes a preamble generation section that generates a preamble that is to be deployed at the top of a transmission frame and includes header information, a midamble generation section that generates a midamble that is to be deployed in the middle of the transmission frame and includes information of at least part of the header information, and a wireless transmission processing section that transmits the transmission frame including the preamble and the midamble. The present technology can be applied to a wireless communication apparatus.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.16/624,299, filed Dec. 19, 2019, which is based on PCT filingPCT/JP2018/023766, filed Jun. 22, 2018, which claims priority to JP2017-132694, filed Jul. 6, 2017, the entire contents of each areincorporated herein by reference.

TECHNICAL FIELD

The present technology relates to a wireless communication apparatus andmethod, and particularly to a wireless communication apparatus andmethod by which communication can be performed with a higher efficiency.

BACKGROUND ART

In recent years, research and development of a high density wireless LAN(Local Area Network) system have been and are being done, and methodsfor applying an advanced space reuse (Spatial Reuse) technology thatincreases the capacity of existing wireless LAN terminals to implement ahigh throughput have been invented.

Among such methods, as an advanced space reuse (Spatial Reuse)technology, a technology has been invented which allows coexistence of asignal of a basic service set (BSS (Basis Service Set)) of a wirelesscommunication apparatus itself and a signal from an overlap basicservice set (OBSS (Overlapping Basic Service Set)) existing in theneighborhood of the wireless communication apparatus itself. Inparticular, for example, a communication method has been invented whichcarries out, if a signal from an OBSS neighboring with a wirelesscommunication apparatus itself has a predetermined reception electricfield strength (reception power) or less, then transmission of a signalof the wireless communication apparatus itself within a range withinwhich the transmission does not have an influence on the OBSS.

Further, a technology is generally known which inserts a midamble forresynchronization in the middle of a frame of transmission data tocorrect a phase, a frequency error and so forth of the frame configuredfrom a long information amount.

As such a technology as just described, a technology is available bywhich, for example, an MSDU (MAC (Media Access Control) Service DataUnit) into MPDUs (MAC Protocol Data Units) determined in advance and asub frame to which a PHY (Physical layer) preamble is added is deployedat the top MPDU while, to each succeeding MPDU, a sub frame to which amidamble is added is configured to perform data transmission (forexample, refer to PTL 1).

Also a technology has been proposed by which a training field is addedto each n OFDM (Orthogonal Frequency Division Multiplexing) symbols toconfigure successive frames (for example, refer to PTL 2). In thistechnology, the training field part is a midamble.

The technologies mentioned adopt a configuration that a training fieldis deployed for each n OFDM symbols determined in advance.

Further, the technologies adopt a configuration that a single VHT SIG-Afield that is added to the preceding stage to the training field isdeployed at the succeeding stage and only one VHT SIG-B field that isadded to the succeeding stage of the training field is deployed only atthe top portion, and they are accommodated in n OFDM symbols.

Also technologies have been disclosed that, from among training fields,a training field of a LTF (Long Training Field) is deployed for each nOFDM symbols and training fields of another STF (Short Training Field)and a LTF are added for each m OFDM symbols where m is an integermultiple of n.

Among the technologies, also a technology has been disclosed that atraining field and signaling called N-SIG are added to notify an OFDMsymbol number to a next training field.

As described above, in the past, a configuration for adding a midamblefor each predetermined OFDM symbols has been used.

CITATION LIST Patent Literature [PTL 1]

JP 2014-522610T

[PTL 2]

JP 2015-507889T

SUMMARY Technical Problems

However, it is difficult for the technologies described above to performcommunication efficiently.

In particular, in the case where the advanced space reuse technology isapplied, it is prescribed that, even if a signal from a neighboring OBSSis received, a BSS can perform transmission of data. Therefore, in thecase where a signal in the BSS is being received, a state in which itbecomes less likely to grasp a utilization situation of a transmissionline due to signal transmission from a neighboring OBSS is establishedand, on the contrary, it becomes difficult to perform communication inthe BSS of the wireless communication apparatus itself.

In particular, since, during transmission of a frame toward the insideof the BSS of the wireless communication apparatus itself, also signaltransmission from the different OBSS is started, it is difficult tospecify whether the transmission line is being utilized after frametransmission in the BSS of the wireless communication apparatus itselfcomes to an end.

Further, even in the case where a signal level equal to or higher than apredetermined reception electric field strength (reception power) isdetected in regard to a received signal, if the signal is not receivedbeginning with the header part, then it cannot be decided whether thesignal is a signal from an OBSS or a signal from within the BSS.

If it cannot be decided whether the received signal is a signal fromwithin the BSS of the wireless communication apparatus itself or asignal from an OBSS, then it cannot be decided whether or not it ispossible to perform multiplex transmission applying the advanced spacereuse technology and advanced space reuse cannot be performedefficiently. In short, communication cannot be performed efficiently.

Further, even if a signal is detected in the middle of a frame, sinceinformation indicative of the duration (Duration) of the signal cannotbe obtained, reception end time of the frame cannot be grasped.Accordingly, in order to start new signal transmission after an end of aframe detected, detection of the signal level must always be continued.

In the related art configuration that a midamble or a training field isinserted in the middle of a frame, since information of the header partis deployed only at the top of a frame, if the top of the frame cannotbe decoded correctly, then the header information cannot be grasped.This makes it impossible to decide whether a frame being received is asignal from an OBSS or a signal from within the BSS.

The present technology has been made in view of such a situation asdescribed above and makes it possible to perform communication with ahigher efficiency.

Solution to Problems

A wireless communication apparatus of a first aspect of the presenttechnology incudes a preamble generation section configured to generatea preamble that is to be deployed at a top of a transmission frame andincludes header information, a midamble generation section configured togenerate a midamble that is to be deployed in a middle of thetransmission frame and includes information of at least part of theheader information, and a wireless transmission processing sectionconfigured to transmit the transmission frame including the preamble andthe midamble.

A wireless communication method of the first aspect of the presenttechnology includes the steps of generating a preamble that is to bedeployed at a top of a transmission frame and includes headerinformation, generating a midamble that is to be deployed in a middle ofthe transmission frame and includes information of at least part of theheader information, and transmitting the transmission frame includingthe preamble and the midamble.

In the first aspect of the present technology, a preamble that is to bedeployed at the top of a transmission frame and includes headerinformation is generated, and a midamble that is to be deployed in themiddle of the transmission frame and includes information of at leastpart of the header information is generated. Then, the transmissionframe including the preamble and the midamble is transmitted.

A wireless communication apparatus according to a second aspect of thepresent technology includes a wireless reception processing sectionconfigured to receive a reception frame that includes a preambledeployed at a top of the reception frame and including headerinformation and a midamble deployed in a middle of the frame andincluding information of at least part of the header information, and amidamble detection section configured to detect the midamble from thereception frame and extract the information of the at least part of theheader information included in the midamble.

A wireless communication method according to the second aspect of thepresent technology includes the steps of receiving a reception framethat includes a preamble deployed at a top of the reception frame andincluding header information and a midamble deployed in a middle of theframe and including information of at least part of the headerinformation, and detecting the midamble from the reception frame andextracting the information of the at least part of the headerinformation included in the midamble.

In the second aspect of the present technology, a reception frame thatincludes a preamble deployed at the top of the reception frame andincluding header information and a midamble deployed in the middle ofthe frame and including information of at least part of the headerinformation is received, and the midamble is detected from the receptionframe. Then, the information of the at least part of the headerinformation included in the midamble is extracted.

Advantageous Effect of Invention

According to the first aspect and the second aspect of the presenttechnology, communication can be performed with a high efficiency.

It is to be noted that the effect described here is not necessarilyrestrictive, and some effects indicated in the present disclosure may beapplicable.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a view depicting a configuration example of a wirelessnetwork.

FIG. 2 is a view depicting a configuration example of a wirelesscommunication apparatus.

FIG. 3 is a view depicting a configuration example of a wirelesscommunication module.

FIG. 4 is a view depicting a general frame format.

FIG. 5 is a view depicting a configuration example of L-SIG.

FIG. 6 is a view depicting a configuration example of HE-SIG-A.

FIG. 7 is a view depicting a configuration example of a transmissionframe for which frame aggregation has been performed.

FIG. 8 is a view depicting configuration examples of a transmissionframe in which a midamble is inserted.

FIG. 9 is a view depicting configuration examples of a transmissionframe in which a midamble is inserted.

FIG. 10 is a view depicting a configuration example of a transmissionframe to which the present technology is applied.

FIG. 11 is a view depicting another configuration example of atransmission frame to which the present technology is applied.

FIG. 12 is a view depicting configuration examples of a midamble.

FIG. 13 is a view depicting configuration examples of a midamble.

FIG. 14 is a view depicting configuration examples of a midamble.

FIG. 15 is a view depicting a configuration example of HE MID.

FIG. 16 is a view illustrating general carrier detection.

FIG. 17 is a view illustrating carrier detection in the presenttechnology.

FIG. 18 is a view illustrating communication by general advanced spacereuse.

FIG. 19 is a view illustrating communication by advanced space reuse inthe present technology.

FIG. 20 is a view illustrating a relationship between reception powerand transmission power.

FIG. 21 is a flow chart illustrating a transmission process.

FIG. 22 is a flow chart illustrating a reception process.

FIG. 23 is a view depicting a configuration example of computer.

DESCRIPTION OF EMBODIMENTS

In the following, embodiments to which the present technology is appliedare described with reference to the drawings.

First Embodiment <Configuration Example of Wireless Network>

The present technology makes it possible to carry out appropriatetransmission control by performing signal transmission in a signalformat that makes it possible, even in the case where a signaltransmitted by wireless communication is detected from the middle of aframe, parameters in header information described in the preamble can bespecified such that the parameters can be specified. Consequently,communication can be carried out with a higher efficiency.

In particular, a midamble to be inserted in the middle of a frame isconfigured so as to include part of header information such that, on thereception side, in the case where the midamble is detected, headerinformation included in the midamble can be extracted by decoding, forexample, the first OFDM midamble immediately after the detection.

The header information includes, for example, BSS Color information foridentifying the BSS, parameters relating to an advanced space reusetechnology (Spatial Reuse), information indicative of a state oftransmission power controlling operation and so forth, and the receptionside of the signal can perform appropriate decision from the informationmentioned.

Further, in the header information, parameters of information of amodulation method and an encoding scheme (MCS (Modulation and CodingScheme)), information of the remaining time and the data length of aframe (Length) and so forth may be suitably deployed in the data part.

Furthermore, a midamble may be deployed in a unit of a MAC Protocol DataUnit (MPDU), namely, in a unit of a sub frame, such that the necessityfor performing a padding process at the tail end of an MPDU iseliminated also when aggregation is carried out with a plurality ofMPDUs.

Since this makes it possible to perform decoding in a unit of a subframe beginning with the middle of a frame even in the case where MPDUaggregation is carried out, even if header information at the preamblepart is missed, the header information can be received from a middle oneof the MPDUs.

In the following, a particular embodiment in which the presenttechnology is applied is described. FIG. 1 is a view depicting aconfiguration example of a wireless network including a wirelesscommunication apparatus to which the present technology is applied.

In the example depicted in FIG. 1, a relationship between a wirelesscommunication apparatus to which the present technology is applied andwireless communication apparatus existing around the wirelesscommunication apparatus is depicted.

In particular, a wireless communication apparatus STA0 cooperates withan access point AP1 of a first basic service set to which the wirelesscommunication apparatus STA0 itself belongs, namely, of the BSS(hereinafter referred to as BSS 1) and a different wirelesscommunication apparatus STA1 to establish a wireless network to carryout communication.

In other words, to the BSS 1 that is a wireless network, the wirelesscommunication apparatus STA0, access point AP1, and wirelesscommunication apparatus STA1 belong, and they configure a wirelesscommunication system.

In the present example, whether a detected signal is a signaltransmitted from an apparatus that configures the BSS 1 can be specifiedfrom BSS Color information=0x01 indicative of the BSS 1 included in thesignal. The BSS Color information is information for specifying awireless network to which an apparatus of a transmission source of thesignal in which the BSS Color signal is included belongs.

Further, around the wireless communication apparatus STA0, also anaccess point AP2 of a second BSS (hereinafter referred to as OBSS 2)that exists around the wireless communication apparatus STA0 andoverlaps with the BSS 1 and a wireless communication apparatus STA2exist. Here, whether a detected signal has been transmitted from anapparatus that configures the OBSS 2 can be specified from BSS colorinformation=0x02 that is included in the signal and indicates the OBSS2.

Furthermore, around the wireless communication apparatus STA0, also anaccess point AP3 of a third BSS (hereinafter referred to as the OBSS 3)that exists around the wireless communication apparatus STA0 andoverlaps with the BSS 1 and a wireless communication apparatus STA3exist. Here, whether a detected signal has been transmitted from anapparatus that configures the OBSS 3 can be specified from BSS colorinformation=0x03 that indicates the OBSS 3 included in the signal.

In the case where the OBSS 2 or the OBSS 3 having a communicatable rangeoverlapping with that of the BSS 1 exists in such a manner, for example,the wireless communication apparatus STA0 detects not only a signaltransmitted from the access point AP1 or the wireless communicationapparatus STA1 configuring the BSS 1 but also a signal transmitted fromsuch an apparatus as the access point AP2, the wireless communicationapparatus STA2, the access point AP3, or the wireless communicationapparatus STA3.

Each of the BSSes including the BSS 1, the OBSS 2, and the OBSS 3 isconfigured such that it carries out transmission power control toperform communication in response to a situation between the apparatusthat configure the BSS.

For example, in the OBSS 2 configured from the access point AP2 and thewireless communication apparatus STA2 in which the communicationsituation is better than that in the BSS 1, communication is performedwith transmission power reduced. Further, in the OBSS 3 in which theaccess point AP3 and the wireless communication apparatus STA3 in whichthe communication situation is worse than that in the BSS 1,communication is performed with transmission power increased.

In short, each BSS is configured such that transmission power controlaccording to the apparatus that configure the wireless network (BSS) iscarried out. Therefore, since communication is not carried out withpredetermined transmission power as before and whether or not atransmission line is utilized cannot be determined uniquely from thereception electric field strength (reception power) of the receivedsignal, it is difficult to carry out transmission control by CSMA/CA(Carrier Sense Multiple Access/Collision Avoidance).

Further, in recent years, it has been conceived to improve theutilization efficiency of a wireless transmission line by performing theadvanced space reuse technology, for example, upon communication betweenthe access point AP3 and the wireless communication apparatus STA3 ofthe OBSS 3, communication in which the transmission power from thewireless communication apparatus STA0 to the access point AP1 iscontrolled is performed so as not to have an influence on thecommunication.

In short, each BSS is configured such that it carries out advanced spacereuse by carrying out communication in the BSS of the wirelesscommunication apparatus itself and unrelated communication of anoverlapping BSS (OBSS) in an overlapping relationship with each other.

However, if communication from the wireless communication apparatus STA0to the access point AP1 is carried out, then since this has a biginfluence on communication between the access point AP2 and the wirelesscommunication apparatus STA2 of the OBSS 2 that are communicating witheach other with transmission power of the wireless communicationapparatus itself, control for refraining from transmission is required.

<Configuration Example of Wireless Communication Apparatus>

Now, a configuration of the apparatus configuring the BSSes depicted inFIG. 1 is described.

FIG. 2 is a view depicting a configuration example of a wirelesscommunication apparatus to which the present technology is applied.

A wireless communication apparatus 11 depicted in FIG. 2 corresponds tosuch apparatus as, for example, the wireless communication apparatusSTA0, the wireless communication apparatus STA1, and the access pointAP1 that configure the BSS 1 depicted in FIG. 1.

It is to be noted that the description here is given assuming that thewireless communication apparatus 11 is configured such that it canoperate as any of an access point such as the access point AP1 and acommunication device such as the wireless communication apparatus STA0,which configure the BSS, namely, the wireless LAN system. However, thewireless communication apparatus 11 may naturally be configured suchthat components unnecessary for individual operations are omitted asoccasion demands.

The wireless communication apparatus 11 includes, for example, anInternet connection module 21, an information inputting module 22, anapparatus controlling section 23, an information outputting module 24,and a wireless communication module 25.

The Internet connection module 21 functions as an adapter that isconnected by wire connection to the Internet network, for example, whenthe wireless communication apparatus 11 operates as an access point. Inparticular, the Internet connection module 21 supplies data receivedthrough the Internet network to the apparatus controlling section 23 andtransmits data supplied from the apparatus controlling section 23 to acommunication partner through the Internet.

The information inputting module 22 acquires, in the case where, forexample, a button or the like is operated by a user to input anoperation desired by the user, a signal according to the operation ofthe user and supplies the signal to the apparatus controlling section23. For example, in the case where various buttons and switches, a touchpanel, a mouse, a keyboard and so forth are operated by the user, or inthe case where the user performs an inputting operation with voice orthe like to a microphone or the like, the information inputting module22 decides such operation input and acquires a signal supplied inresponse to the operation.

The apparatus controlling section 23 controls operation of the overallwireless communication apparatus 11 in response to a signal or the likesupplied from the information inputting module 22. In particular, theapparatus controlling section 23 includes a CPU (Central ProcessingUnit) that centrally manages control of operation of the wirelesscommunication apparatus 11 and executes arithmetic processing, blocksfor implementing functions corresponding to an OS (Operating System) andso forth.

For example, the apparatus controlling section 23 supplies predetermineddata to the wireless communication module 25 so as to transmit the datato a communication partner by wireless communication and acquires datareceived from the communication partner from the wireless communicationmodule 25. Further, the apparatus controlling section 23 suppliesinformation to the information outputting module 24 such that theinformation is displayed.

The information outputting module 24 includes, for example, a display, aspeaker and so forth and outputs information supplied thereto from theapparatus controlling section 23 to the user. For example, theinformation outputting module 24 causes information supplied from theapparatus controlling section 23 to be displayed on a display providedin the information outputting module 24 itself or the like to presentdesired information to the user.

The wireless communication module 25 operates as a communication modulefor allowing the wireless communication apparatus 11 to actually carryout wireless communication operation. In particular, the wirelesscommunication module 25 transmits data supplied from the apparatuscontrolling section 23 with frames of a predetermined format by wirelesscommunication, and receives a signal transmitted thereto by wirelesscommunication and supplies data extracted from the received signal tothe apparatus controlling section 23.

<Configuration Example of Wireless Communication Module>

The wireless communication module 25 of the wireless communicationapparatus 11 is configured, for example, in such a manner as depicted inFIG. 3.

The wireless communication module 25 depicted in FIG. 3 includes aninterface 51, a transmission buffer 52, a network management section 53,a transmission frame construction section 54, a wireless communicationcontrolling section 55, a header information generation section 56, amidamble generation section 57, a transmission power controlling section58, a wireless transmission processing section 59, an antennacontrolling section 60, an antenna 61, a wireless reception processingsection 62, a detection threshold value controlling section 63, amidamble detection section 64, a header information analysis section 65,a reception data construction section 66, and a reception buffer 67.

The interface 51 is connected to a different module configuring thewireless communication apparatus 11 such as, for example, the apparatuscontrolling section 23 such that it supplies data supplied from thedifferent module to the transmission buffer 52 and supplies dataretained in the reception buffer 67 to the different module. Further,the interface 51 supplies information supplied from a different modulesuch as the apparatus controlling section 23 and supplies informationsupplied from the network management section 53 to the different modulesuch as the apparatus controlling section 23.

The transmission buffer 52 retains data supplied from the interface 51and supplies the retained data to the transmission frame constructionsection 54.

For example, data retains in the transmission buffer 52 is data to bestored into a MAC layer protocol data unit (MPDU) for performingwireless transmission.

The network management section 53 manages a network that overlaps withthe wireless communication apparatus itself with ambient wirelesscommunication apparatus. In particular, the network management section53 supplies information supplied from the interface 51 or the receptiondata construction section 66 to the wireless communication controllingsection 55. Further, the network management section 53 instructs thetransmission frame construction section 54 to construct a frameconfigured from a predetermined number of MPDUs and instructs thereception data construction section 66 to construct data in apredetermined unit.

The transmission frame construction section 54 places data retained inthe transmission buffer 52 into an MPDU in accordance with aninstruction from the network management section 53 and connects aplurality of MPDUs to construct a wireless communication frame in apredetermined aggregation unit for wireless communication.

The transmission frame construction section 54 supplies a constructedwireless communication frame as a transmission frame to the wirelesstransmission processing section 59 and supplies necessary informationrelating to the transmission frame to the header information generationsection 56.

It is to be noted that, in the following description, a wirelesscommunication frame transmitted by the wireless communication apparatus11 is referred to specifically as transmission frame, and data placed inan MPDU of the transmission frame is hereinafter referred to also astransmission data. Further, a wireless communication frame received bythe wireless communication apparatus 11 is referred to specifically asreception frame, and data placed in an MPDU of the reception frame isreferred to also as reception data.

The wireless communication controlling section 55 carries out accesscommunication control on a wireless transmission line in accordance witha predetermined communication protocol.

In particular, the wireless communication controlling section 55controls the components of the wireless communication module 25 inaccordance with information and so forth supplied from the networkmanagement section 53, the midamble detection section 64, the headerinformation analysis section 65 and so forth to control transmission andreception by wireless communication.

For example, the wireless communication controlling section 55 suppliesnecessary information to the header information generation section 56,the midamble generation section 57, the transmission power controllingsection 58, the antenna controlling section 60, and the detectionthreshold value controlling section 63 to control various operationsrelating to wireless communication and supplies information relating tothe network obtained from received signals and so forth to the networkmanagement section 53.

The header information generation section 56 generates a preambleincluding header information on the basis of information supplied fromthe transmission frame construction section 54 and the wirelesscommunication controlling section 55 and supplies the midamblegeneration section 57 and the wireless transmission processing section59. In other words, the header information generation section 56functions as a preamble generation section that generates a preambleincluding header information.

The preamble generated in such a manner is added to the top portion of atransmission frame. It is to be noted that, from the header informationgeneration section 56 to the midamble generation section 57, onlynecessary information from within the information included in thepreamble is supplied.

The midamble generation section 57 generates a midamble on the basis ofinformation supplied from the header information generation section 56and the wireless communication controlling section 55 and supplies themidamble to the wireless transmission processing section 59.

The midamble includes information of at least part of header informationgenerated by the header information generation section 56 andinformation of at least part of information included in the preamblegenerated by the header information generation section 56 but other thanthe header information. Further, the midamble is inserted into (deployedat) the middle of a transmission frame.

The transmission power controlling section 58 controls the wirelesstransmission processing section 59 and the antenna controlling section60 in accordance with an instruction from the wireless communicationcontrolling section 55 to adjust (control) the transmission power of atransmission frame to be transmitted to a different apparatus thatcommunicates by wireless communication with the wireless communicationapparatus 11 as occasion demands. In short, the transmission powercontrolling section 58 controls operation of the wireless transmissionprocessing section 59 and the antenna controlling section 60 such that atransmission frame is transmitted with predetermined transmission power.

The wireless transmission processing section 59 adds a preamble suppliedfrom the header information generation section 56 and a midamblesupplied from the midamble generation section 57 to appropriatepositions of a transmission frame supplied from the transmission frameconstruction section 54 to generate a final transmission frame.

Further, the wireless transmission processing section 59 converts theobtained transmission frame into a predetermined baseband signal andperforms modulation processing and signal processing on the basis of thebaseband signal, and supplies a resulting transmission signal to theantenna controlling section 60. In particular, the wireless transmissionprocessing section 59 transmits a transmission signal (transmissionframe) to the antenna controlling section 60 and the antenna 61.

The antenna controlling section 60 controls the antenna 61 to output(transmit) a transmission signal supplied from the wireless transmissionprocessing section 59 under the control of the transmission powercontrolling section 58. Further, the antenna controlling section 60supplies a reception signal received by the antenna 61 to the wirelessreception processing section 62.

The antenna 61 is configured from a plurality of elements, and transmitsa transmission signal supplied from the antenna controlling section 60by wireless transmission and supplies a reception signal transmittedthereto to the antenna controlling section 60.

The wireless reception processing section 62 compares a detectionthreshold value supplied from the detection threshold value controllingsection 63 and reception power of a reception signal supplied from theantenna controlling section 60 to receive the reception signaltransmitted by wireless transmission in a predetermined format as areception frame through the antenna 61 and the antenna controllingsection 60.

The detection threshold value controlling section 63 determines adetection threshold value to be used by the wireless receptionprocessing section 62 while transferring necessary information to andfrom the wireless communication controlling section 55 and thetransmission power controlling section 58 and supplies the determineddetection threshold value to the wireless reception processing section62. This detection threshold value is used to detect a preamble and amidamble included in a received signal.

The midamble detection section 64 detects a midamble added to the middleof a frame (reception frame) of a reception signal received by thewireless reception processing section 62 and supplies informationextracted from the midamble to the wireless communication controllingsection 55 and the header information analysis section 65.

The header information analysis section 65 detects a preamble added tothe top of a frame (reception frame) of a reception signal received bythe wireless reception processing section 62, and extracts headerinformation from the preamble and analyzes the description of the headerinformation. Further, as occasion demands, the header informationanalysis section 65 analyzes the description of part of the headerinformation extracted from a midamble by the midamble detection section64. Further, the header information analysis section 65 supplies theinformation included in the extracted header information to the wirelesscommunication controlling section 55 and the reception data constructionsection 66.

In short, the header information analysis section 65 functions as apreamble detection section that detects a preamble from a receptionframe and extracts header information and so forth from the detectedpreamble.

The reception data construction section 66 constructs, on the basis ofinformation supplied from the header information analysis section 65, areception signal received by the wireless reception processing section62, namely, an aggregated reception frame, in a predetermined unit asreception data. The reception data construction section 66 supplies theconstructed reception data to the network management section 53 and thereception buffer 67.

The reception buffer 67 retains reception data supplied form thereception data construction section 66 and supplies the retainedreception data to the interface 51. The data retained in the receptionbuffer 67 is reception data extracted from a MAC layer protocol dataunit (MPDU) of a reception frame.

<Examples of Frame Format>

Here, the format of a signal transferred between wireless communicationapparatus is described.

For example, in the case where frame aggregation is not performed,generally a transmission frame of a frame format depicted in FIG. 4 istransferred between wireless communication apparatus.

In the example depicted in FIG. 4, a preamble is deployed at the top ofdata for one frame of a transmission frame and is followed bytransmission data.

In particular, in the preamble, L-STF, L-LTF, L-SIG, RL-SIT, HE-SIG-A,HE-STF, and a predetermined number of HE-LTF are deployed in order.

Here, L-STF is conventionally called short training field (Legacy ShortTraining Field), and is utilized a reference for start detection of atransmission frame and time synchronization processing and is utilizedalso for estimation of a frequency error and automatic gain control(Automatic Gain Control). Since this L-STF is configured such that apredetermined sequence is repeated, a wireless communication apparatuson the reception side can detect a start position of a transmissionframe by detecting a correlation of the sequence.

L-LTF is conventionally called long training field (Legacy Long TrainingField) and is configured such that a predetermined sequence is repeated.L-LTF is utilized to carry out channel estimation and estimation of theS/N (Signal/Noise) ratio as well as synchronization between time and afrequency.

L-SIG is conventionally called signal (Legacy Signal) field and issignaling information configured such that rate information and lengthinformation of the data part are described in the OFDM symbol at thetop.

RL-SIG is information (signaling information) set in order to detectthat the transmission frame is not a frame of a method of a precedinggeneration but is HE-PPDU.

This RL-SIG is information quite same as L-SIG, and a transmission frameis configured such that L-SIG and RL-SIG are deployed successively and,as a result, L-SIG is equivalently deployed repeatedly.

A wireless communication apparatus on the reception side can specify, bydetecting L-SIG and RL-SIG deployed successively, that the transmissionframe is of a format of a predetermined generation, namely, is atransmission frame of the frame format depicted in FIG. 4.

HE-SIG-A is, as the A field of the signal in a high density system,information (signaling information) in which information for allowingapplication of a spatial multiplexing technology is deployed.

The wireless communication apparatus is configured such thatpredetermined communication is carried out in accordance with parametersincluded in this HE-SIG-A, and although parameters relating to BSS Colorinformation and Spatial Reuse are described in HE-SIG-A, further variousparameters are included in HE-SIG-A as occasion demands.

The part including L-SIG, RL-SIG, and HE-SIG-A in the preambleconfigures header information.

Meanwhile, HE-STF is a short training field (High Efficiency ShortTraining Field) in the high density system and is utilized forsynchronization processing and adjustment of physical layer parameters,which are required to achieve high density.

HE-LTF is a long training field (High Efficiency Long Training Field) inthe high density system.

This HE-LTF is configured such that, in the case where transmission by aspatial multiplexed stream by MIMO (Multiple Input Multiple Output) isto be carried out, a number of trainings corresponding to the spatialmultiplexed stream number is deployed. In short, a predetermined numberof HE-LTF are deployed after HE-STF.

The part from L-STF to HE-LTF described above configures a preambledeployed at the top of a transmission frame. A wireless communicationapparatus on the reception side can grasp that a transmission frame istransmitted thereto by detecting such a preamble part as just described.

Further, Data following the preamble indicates transmission data, and PE(Packet Extension) is deployed at the tail end of the transmission framefollowing the transmission data as occasion demands.

It is to be noted that the long training field (LTF) such as L-LTF andHE-LTF may be configured from a training sequence part and a guardinterval part. Further, the long training field may be configured suchthat one guard interval is included in two OFDM symbols or may beconfigured such that two guard intervals are included in two OFDMsymbols.

Furthermore, L-SIG depicted in FIG. 4 is configured, for example, insuch a manner as depicted in FIG. 5.

In the example depicted in FIG. 5, L-SIG includes rate informationindicated by character “RATE,” length information indicated by character“LENGTH,” a parity bit indicated by character “P,” tail bit informationindicated by character “Tail” and so forth.

The rate information is information indicative of a rate (bit rate) oftransmission data indicated by character “Data” depicted in FIG. 4, andthe length information is information indicative of a length oftransmission data indicated by character “Data” depicted in FIG. 4.

Meanwhile, HE-SIG-A depicted in FIG. 4 is configured, for example, insuch a manner as depicted in FIG. 6.

In the example depicted in FIG. 6, HE-SIG-A includes, as representativeparameters relating to the present technology, uplink/downlinkidentifier information indicated by character “UL/DL,” MCS parameterinformation indicated by character “MCS,” BSS color informationindicated by character “BSS Color,” parameter information relating tothe advanced space reuse technology indicated by character “SpatialReuse,” bandwidth information indicated by character “Bandwidth,”parameter information of a size of a guard interval and a training fieldindicated by character “GI+TF Size,” spatial multiplexed stream numberinformation indicated by character “Nsts,” duration information of atransmission opportunity indicated by character “TXOP Duration,” anerror detection code (CRC (Cyclic Redundancy Check)) indicated bycharacter “CRC,” tail bit information indicated by character “Tail” andso forth.

For example, the MCS parameter is information indicative of a modulationmethod and an encoding scheme of transmission data (transmission frame),and the BSS color information is information indicative of the BSS towhich an apparatus of a transmission source of transmission databelongs.

<Configuration Example of Frame upon Frame Aggregation>

Furthermore, in the case where frame aggregation is performed, a generalframe configuration of a transmission frame is such as depicted in FIG.7.

FIG. 7 depicts an example in which four MAC layer protocol data units(MPDUs) are aggregated (connected) into a single transmission frame.

Here, following the preamble (Preamble) at the top of the transmissionframe aggregated, four MPDUs denoted by “MPDU-1” to “MPDU-4” aredeployed, and delimiter information indicated by character “D” isdeployed immediately preceding to each MPDU.

The preamble includes a predetermined legacy training field, PHY headerinformation, and a training field for a predetermined space multiplexedstream, and the four MPDUs are combined with this preamble to configureone transmission frame.

Further, the delimiter information deployed immediately preceding toeach MPDU includes MPDU length information indicated by character “MPDULength” and CRC, and the MPDU length information indicates aninformation length, namely, a length, of the MPDU deployed immediatelyfollowing the delimiter information.

Furthermore, in each MPDU, MAC header information indicated by character“MAC Header” is deployed at the top portion of the MPDUs. In this MACheader information, address information indicted by character “Address”and Duration information indicated by character “Duration” are deployed.

Here, the address information is information indicative of an addressfor identifying a destination of the MPDU, namely, an apparatus of atransmission destination of the transmission frame or an address foridentifying an apparatus of a reception destination, and the Durationinformation is information indicative of a duration of the MPDU. Inshort, communication (transmission and reception) of the MPDU isperformed only for the duration indicated by the Duration information.

In the MPDU, next to the MAC header information, a payload indicated bycharacter “MAC Data Payload,” namely, transmission data deployed in theMPDU, is deployed. This payload has a variable length.

In the MPDU, next to the MAC header information, namely, at the last end(tail end) of the MPDU, a frame check sequence (FCS (Frame CheckSequence)) indicated by character “FCS” is deployed. This frame checksequence makes it possible for the reception side of the transmissionframe to perform error detection.

A plurality of MPDUs in which variable length data is deployed isaggregated to form a transmission frame (burst) in such a manner asdescribed above, and the resulting transmission frame can betransmitted.

Incidentally, technologies for inserting a midamble forresynchronization to the middle of a transmission frame have beenproposed already, and among them, technologies that adopt such midambledeployments as depicted in FIGS. 8 and 9 have been proposed.

For example, the examples indicated by an arrow mark Q11 and anotherarrow mark Q12 in FIG. 8 are configured such that a training field isinserted in a long data unit.

In particular, transmission data are placed in a portion of OFDM symbols(plural) indicated by character “Data Sym,” and training fields such asVHT LTF (Very High Throughput Long Training Field), VHT STF (Very HighThroughput Short Training Field) and so forth are deployed before thetransmission data.

Especially, it can be recognized that those examples are configured inmost cases such that a training field is added for each n OFDM symbols.In other words, the examples are configured such that a training fieldis inserted into and wirelessly transmitted together with known n OFDMsymbols determined in advance from a wireless communication apparatus onthe transmission side.

In the example indicated by the arrow mark Q11, VHT STF is inserted as amidamble for each n OFDM symbols, and in the example indicated by thearrow mark Q12, VHT STF and a plurality of VHT LTF are inserted as amidamble.

The number of OFDM symbols in which such training fields as VHT STF andVHT LTF are inserted is grasped also by the reception side. According,the wireless communication apparatus on the reception side can extract,after it extracts the predetermined number of OFDM symbols after an endof the training field in the header, the training field as the midambleinserted in the middle.

Meanwhile, in the example indicated by the arrow mark Q21 in FIG. 9, aplurality of VHT LTF is inserted for each n OFDM symbols, and where m isan integer multiple of the number n of OFDM symbols in which VHT LTF isinserted, VHT STF is inserted for each multiple m. Also in this example,training fields such as VHT LTF and VHT STF are inserted as a midamble.

Also it has been proposed to deploy N-SIG after a training field such asVHT LTF or VHT STF as indicated by an arrow mark Q22. In this example,N-SIG is information indicative of whether a next training field existsat a position n OFDM symbols ahead.

<Configuration Example of Frame to which Present Technology is Applied>

In such examples depicted in FIGS. 8 and 9 as described above, a frameconfiguration that a midamble configured from a training field isinserted in the middle of a transmission frame is adopted.

However, a training field deployed in the middle of a transmission frameis deployed for the object of correcting symbol synchronization orfrequency error. Therefore, when a transmission frame is receivedbeginning with the middle thereof, parameters described in headerinformation deployed at the top portion of the transmission frame cannotbe obtained.

Therefore, in the present technology, in a midamble inserted in themiddle of a transmission frame, not only a training field but also atleast part of information (parameters) included in header information inthe preamble of the transmission frame are placed.

Such a transmission frame to which the present invention is applied asdescribed above has, for example, such a configuration as depicted inFIG. 10.

In the example depicted in FIG. 10, a preamble indicated by character“Preamble” is deployed at the top of the transmission frame and isfollowed by an aggregated MPDU indicated by characters “MPDU-1” to“MPDU-4.” Further, between each adjacent ones of the MPDUs in the middleof the transmission frame, a midamble including a training fieldindicated by character “Mid TF” is inserted (deployed).

In other words, the transmission frame is configured such that apreamble is added to the top of a portion configured from a plurality ofMPDUs and a midamble is inserted between adjacent ones of the MPDUs. Inshort, a midamble is deployed for each MPDU.

It is to be noted that, although the insertion position of a midamblecan be an arbitrary position such as a position after each number ofOFDM symbols determined in advance, in the case where a plurality ofMPDUs is aggregated to configure a transmission frame, a midamble may beinserted at an end of an OFDM symbol for each end of an MPDU, namely, ina unit of an MPDU. Especially in this example, the transmission frame isconfigured such that a midamble is inserted in a unit of an MPDU unit.

In a general transmission frame, since a midamble has been deployed foreach predetermined number of OFDM symbols, reception processing has notbeen able to converge for each MPDU. Therefore, separately frominformation indicative of the information length of an MPDU, informationfor transmitting the number of OFDM symbols into which a midamble is tobe inserted has been necessitated.

Further, in a general transmission frame, the number of OFDM symbolsinto which a midamble is inserted and the information length of an MPDUhave no clear correlation therebetween. Therefore, in the case where aplurality of MPDUs is aggregated into one transmission frame, a processfor grasping a midamble insertion position and stopping decoding of areceived transmission frame is necessitated.

In contrast, by deploying a midamble in a unit of an MPDU as in theexample depicted in FIG. 10, the necessity for information fortransmitting the number of OFDM symbols is eliminated, and thecommunication efficiency can be improved. Further, since a midamble isnot deployed in the middle of an MPDU, processing such as decoding canbe performed simply in a unit of an MPDU.

In the preamble deployed at the top of a transmission frame, L-STF,L-LTF, L-SIG, RL-SIG, HE-SIG-A, HE-STF, and a predetermined number ofHE-LTF are deployed in order from the top, and the deployment of theinformation is same as that in the case of the preamble of thetransmission frame depicted in FIG. 4. Further, in the preamble part,L-STF, L-LTF, HE-STF, and HE-LTF are information for training, and theportion of L-SIG, RL-SIG, and HE-SIG-A is header information.

In order to keep compatibility with existing products, namely, in orderto keep compatibility with the standards in preceding generations, thepreamble has deployed therein L-STF that is legacy STF, L-LTF that islegacy LTF, L-SIG that is legacy SIGNAL, and RL-SIG that is repetitionsof L-SIG.

Further, in the preamble, at positions after L-STF, L-LTF, L-SIG, andRL-SIG, HE-STF that is STF (short training field) of the high densitysystem and HE-LTF that is LTF (long training field) of the high densitysystem are deployed. Especially here, a predetermined number of HE-LTFare deployed successively.

In the example of FIG. 10, following the preamble, one MPDU indicated bycharacter “MPDU-1” is deployed, and transmission data is placed in theMPDU. Here, each MPDU that is a data part has a length of delimited OFDMsymbols determined in advance. This MPDU has a configuration same asthat of the MPDU depicted in FIG. 7, and MAC header information in whichaddress information and Duration information are placed is deployed atthe top of the MPDU and transmission data, namely, a payload, isdeployed next to the MAC header information.

Further, next to the MPDU, a midamble indicated by character “Mid TF” isdeployed, and in this midamble, at least part of the informationincluded in the preamble deployed at the top of the transmission frameis placed.

In other words, the midamble includes information of at least part ofthe header information in the preamble and information of at least partof the information other than the header information in the preamble.Here, the information other than the header information included in thepreamble is information for a training field such as L-STF, L-LTF,HE-STF, and HE-LTF, namely, for training.

In the example depicted in FIG. 10, in the midamble, L-STF, L-LTF,L-SIG, HE MID, HE-STF, and a predetermined number of HE-LTF are deployedin order from the top.

Especially here, a number of HE-LTF equal to that in the case of thepreamble are deployed in a successively lined up relationship in themidamble, and the positional relationship in deployment of L-STF, L-LTF,L-SIG, HE-STF, and HE-LTF is a same positional relationship as that inthe case of the preamble.

In other words, L-STF, L-LTF, L-SIG, HE-STF, and HE-LTF that areinformation included in common in the preamble and the midamble aredeployed in a same order and in a same number in the preamble and themidamble.

It is to be noted that an example in which information included incommon in the preamble and the midamble is common in deployment in thepreamble and the midamble is described here. However, the informationincluded in common in the preamble and the midamble may otherwise bedifferent in deployment in the preamble and the midamble.

In the midamble, L-STF, L-LTF, HE-STF, and HE-LTF are placed asinformation for training, and L-SIG and HE MID are placed as part of theinformation included in the header information.

Here, L-SIG is information, for example, of the configuration depictedin FIG. 5, and in L-SIG, the rate information and the length informationdescribed hereinabove are placed. Further, HE MID is midambleinformation of the high density system, and in this HE MID, part ofinformation included in HE-SIG-A in the header information and so forthare placed. It is to be noted that details of HE MID are hereinafterdescribed.

Further, in the example of FIG. 10, following the midamble deployedimmediately after an MPDU indicated by character “MPDU-1,” an MPDUindicated by character “MPDU-2,” a midamble, an MPDU indicated bycharacter “MPDU-3,” a midamble, and an MPDU indicated by character“MPDU-4” are deployed in order.

Accordingly, in the case where the transmission frame depicted in FIG.10 is to be transmitted, the preamble is transmitted first, and thenafter one MPDU is transmitted, a midamble is transmitted. Thereafter, anMPDU and a midamble are transmitted alternately in order until the tailend of the aggregated frame is reached.

It is to be noted that, although an example in which a midamble (Mid TF)is inserted for each predetermined length is described here, a midamblemay be inserted for each variable length MPDU.

In such a case as just described, it is sufficient if delimiterinformation is deployed immediately before each MPDU, for example, asdepicted in FIG. 11 such that the length of each MPDU can be specified.

In the example depicted in FIG. 11, a preamble indicated by character“Preamble” is deployed at the top of the transmission frame, and anaggregated MPDU indicated by characters “MPDU-1” to “MPDU-4” is deployednext to the preamble. Here, the information length of each MPDU is avariable length. Further, between each adjacent ones of the MPDUs, amidamble indicated by character “Mid TF” is inserted, and delimiterinformation indicated by character “D” is inserted immediately beforeeach MPDU.

In the transmission frame depicted in FIG. 11, although the deploymentof the preamble, MPDUs, and midambles is same as that in the example ofthe transmission frame depicted in FIG. 10, in the transmission framedepicted in FIG. 11, delimiter information is further deployedimmediately before each MPDU.

For example, the delimiter information deployed immediately before theMPDU indicated by character “MPDU-1” includes MPDU length informationindicative of an information length of the MPDU deployed immediatelyafter the delimiter information, namely, a length of the MPDU. Inparticular, for example, the delimiter information is information havingthe configuration depicted in FIG. 7, and includes MPDU lengthinformation and CRC.

Accordingly, on the reception side of the transmission frame, since thelength of an MPDU immediately after delimiter information can bespecified by the delimiter information, the position of the midambleplaced after the MPDU, namely, the insertion position of the midamble,can be specified.

It is to be noted that, in the example depicted in FIG. 11, informationincluded in the preamble and deployment positions of the information aswell as information included in the midambles and deployment positionsof the information are same as those in the case of the example of atransmission frame depicted in FIG. 10.

<Configuration Example of Midamble>

Further, information (fields) placed in a midamble and deployment of theinformation are not limited to those of the examples depicted in FIGS.10 and 11 and may be any information and deployment.

In particular, various variations are supposed in regard to theconfiguration of a midamble, and any configuration may be applied if itincludes HE MID without fail among L-STF, L-LTF, L-SIG, HE MID, HE-STF,and HE-LTF.

In particular, for example, a midamble can be configured in such amanner as to FIGS. 12 to 14.

In the example indicated by an arrow mark Q31 in FIG. 12, in themidamble, L-STF, L-LTF, L-SIG, HE MID, and a predetermined number ofHE-STF are deployed in order from the top. This example is an examplethat does not include HE-STF in the example depicted in FIG. 10 or 11.

Meanwhile, in the example indicated by an arrow mark Q32, L-STF, L-LTF,HE MID, and a predetermined number of HE-STF are deployed in order fromthe top. This example is an example that does not include L-SIG in theexample depicted in FIG. 10 or 11.

In the example indicated by an arrow mark Q33, in the midamble, L-STF,L-LTF, L-SIG, and HE-MID are deployed in order from the top.

Further, in the example indicated by an arrow mark Q34, in the midamble,L-LTF and HE MID are deployed in order from the top. In the exampleindicated by an arrow mark Q35, L-STF, L-LTF, and HE MID are deployed inorder from the top.

Although, in the examples indicated by the arrow marks Q31 to Q33 andQ35, L-STF for detecting synchronism is deployed preferentially at thetop portion of the midamble, in the example indicated by the arrow markQ34, not L-STF but L-LTF is deployed at the top portion of the midamble.

Further, in the example indicated by an arrow mark Q41 in FIG. 13, inthe midamble, L-LTF, L-SIG, HE MID, HE-STF, and a predetermined numberof HE-LTF are deployed in order from the top.

In the example indicated by an arrow mark Q42, in the midamble, L-LTF,L-SIG, HE MID, and a predetermined number of HE-LTF are deployed inorder from the top.

In the example indicated by an arrow mark Q43, in the midamble, L-LTF,L-SIG, and HE MID are deployed in order from the top.

In the example indicated by an arrow mark Q44, in the midamble, HE-STF,a predetermined number of HE-LTF, and HE MID are deployed in order fromthe top.

In the example indicated by an arrow mark Q45, in the midamble, HE-STF,HE MID, and a predetermined number of HE-LTF are deployed in order fromthe top.

In the example indicated by an arrow mark Q46, in the midamble, apredetermined number of HE-LTF and HE MID are deployed in order from thetop.

For example, if, by receiving only HE-LTF, it is possible to performsuch processes as synchronization and a frequency error of atransmission frame, channel estimation and so forth can be performed,then the midamble need not necessarily include legacy L-SFT or L-LTF. Inother words, the midamble may be configured such that L-SFT and L-LTFare omitted, for example, as in the examples indicated by the arrowmarks Q44 to Q46.

Also legacy L-SIG need not necessarily be included in the midamble ifthe information length of an MPDU unit can be grasped from MPDU lengthinformation of delimiter information added to the MPDU. For example, inthe case of the frame configuration in which delimiter information isadded to each MPDU as in the example depicted in FIG. 11, the midamblemay not include L-SIG as in the examples indicated by the arrow marksQ44 to Q46.

Further, for example, in the example indicated by an arrow mark Q51 inFIG. 14, in the midamble, HE-STF, a predetermined number of HE-LTF,L-SIG, and HE MID are deployed in order from the top.

In the example indicated by an arrow mark Q52, in the midamble, HE-STF,L-SIG, HE MID, and a predetermined number of HE-LTF are deployed inorder from the top.

In the example indicated by an arrow mark Q53, in the midamble, apredetermined number of HE-LTF, L-SIG, and HE MID are deployed in orderfrom the top.

In the example indicated by an arrow mark Q54, in the midamble, L-STF,HE MID, L-SIG, HE-STF, and a predetermined number of HE-LTF are deployedin order from the top.

In the example indicated by an arrow mark Q55, in the midamble, L-STF,HE MID, and a predetermined number of HE-LTF are deployed in order fromthe top.

In the example indicated by an arrow mark Q56, in the midamble, HE-STFand HE MID are deployed in order from the top. In the example indicatedby an arrow mark Q57, in the midamble, HE-STF, L-SIG, and HE MID aredeployed in order from the top.

As indicated in FIGS. 12 to 14 described above, various variations areavailable as the midamble, and any information (field) may be placed inthe midamble. In short, a predetermined field may not be included in themidamble as occasion demands. Further, the fields included in themidamble may be arrayed in any array.

<Configuration Example of HE MID>

Now, configuration examples of HE MID to be placed in the midamble towhich the present technology is applied are described.

HE MID is midamble information of the high density system and forms partof training (Mid TF) of the midamble.

HE MID is configured, for example, in such a manner as depicted in FIG.15.

In the example depicted in FIG. 15, HE MID includes rate informationindicated by character “Rate,” Duration information indicated bycharacter “Remaining Duration (Length),” a parity indicated by character“P,” transmission power control level information indicated by character“TPC level,” and number information of HE-LTF indicated by character“Number of HE-LTF.”

It is to be noted that a region indicated by character “R” in HE MIDdepicted in FIG. 15 is a Reserved region.

HE MID further includes information (hereinafter referred to as MCSparameters) relating to a modulation method and an encoding schemeindicated by character “MCS Parameter,” parameters to be applied to theadvanced space reuse technology indicated by character “Spatial Reuse,”BSS Color information indicated by character “BSS Color,” an errordetection code (CRC) indicated by character “CRC,” Tail bit indicated bycharacter “Tail” and so forth.

For example, the rate information is information indicative of a rate(bit rate) of a transmission frame, namely, of transmission data, andthis rate information is information included in L-SIG in headerinformation.

Meanwhile, the Duration information is information indicative of aduration from a midamble in which this Duration information is includedto the last (tail end) of the transmission frame, namely, a remainingtime period until transmission (reception) of the transmission comes toan end.

The transmission power control level information is informationindicative of the level of transmission power when the transmissionframe is transmitted, and the number information of HE-LTF isinformation indicative of the number of HE-LTF included in the midamble.

The MCS parameters are information indicative of a modulation method andan encoding scheme of the transmission frame, and the parameters to beapplied to the advanced space reuse technology are parameters(information) for advanced space reuse, which are necessitated, forexample, to perform transmission of transmission data by the advancedspace reuse technology.

The BSS Color information is identification information for identifyinga BSS to which the wireless communication apparatus from which thetransmission frame has been transmitted belongs, and the CRC is an errordetection code of the midamble part and the Tail bit is a bit stringindicative of the end position of HE MID.

The MCS parameters, parameters to be applied to the advanced space reusetechnology, BSS Color information, and CRC are information included inHE-SIG-A as header information.

Further, in the example depicted in FIG. 15, the front portion of HEMID, namely, the portion from the rate information to the parity has anarray same as the bit array of legacy L-SIG depicted in FIG. 5. Inparticular, in the front portion of HE MID, the rate information,Reserved region, Duration information, and parity are deployed in orderfrom the top similarly as in L-SIG depicted in FIG. 5.

It is to be noted that the configuration of HE MID is not limited to theconfiguration depicted in FIG. 15 and may be any other configuration.For example, in HE MID, information (parameters) other than thosedepicted in FIG. 15 may be placed as occasion demands, or part of theinformation (parameters) depicted in FIG. 15 may not be included in HEMID. Further, also the order in array of the information to be placed inHE MID can be an arbitrary order.

<Improvement of Communication Efficiency by Present Technology>

Incidentally, in a general transmission frame, header information is notincluded except the top portion. Therefore, in the case where a wirelesscommunication apparatus starts reception from the middle of atransmission frame, namely, in the case where a signal is successfullydetected in the middle of a transmission frame during carrier detection,it cannot be specified whether the transmission frame is a signal in theBSS of the wireless communication apparatus itself.

For example, it is assumed that the wireless communication apparatusSTA1 and the wireless communication apparatus STA3 depicted in FIG. 1perform transmission of a transmission frame and the wirelesscommunication apparatus STA0 performs carrier detection as depicted inFIG. 16.

In the example depicted in FIG. 16, the wireless communication apparatusSTA1 transmits a transmission frame FL11 and the wireless communicationapparatus STA3 transmits a transmission frame FL12. Here, it is assumedthat not only transmission of the transmission frame FL11 but alsotransmission of the transmission frame FL12 are being performed at acertain point of time and the transmission frames are frames of ageneral configuration. In other words, the transmission frame FL11 andthe transmission frame FL12 are configured such that a midamble thatincludes part of header information is not inserted therein.

It is assumed that, in such a situation as just described, CSMA isstarted by the wireless communication apparatus STA0 in the middle ofthe frames. In particular, when the wireless communication apparatusSTA0 performs carrier detection, the transmission frame FL11 is detectedin the middle of transmission and also the transmission frame FL12 isdetected in the middle of transmission.

However, since the wireless communication apparatus STA0 has failed todetect the top portion of the transmission frame FL11, namely, since thewireless communication apparatus STA0 has failed to decode the preambleof the transmission frame FL11, the wireless communication apparatusSTA0 cannot acquire BSS Color information in the header informationincluded in the preamble portion.

Therefore, the wireless communication apparatus STA0 cannot specifywhether the transmission frame FL11 has been transmitted from a wirelesscommunication apparatus in the BSS 1 of the wireless communicationapparatus STA0 itself or has been transmitted from a wirelesscommunication apparatus in a neighboring OBSS. In the present example,the transmission frame FL11 is a signal of the BSS 1 of the wirelesscommunication apparatus STA0 itself.

Similarly, since the wireless communication apparatus STA0 has failed todetect the top portion of the transmission frame FL12, the wirelesscommunication apparatus STA0 cannot acquire BSS Color information of thetransmission frame FL12. Therefore, the wireless communication apparatusSTA0 cannot specify whether the transmission frame FL12 has beentransmitted from a wireless communication apparatus in the BSS 1 of thewireless communication apparatus STA0 itself or has been transmittedfrom a wireless communication apparatus of a neighboring OBSS. In thepresent example, the transmission frame FL12 is a signal of the OBSS 3neighboring with the BSS 1 of the wireless communication apparatus STA0itself.

In such a case as described above, if the wireless communicationapparatus STA0 had succeeded in acquisition of BSS Color information,the wireless communication apparatus STA0 could have performedtransmission of a transmission frame FL13, which is to be transmitted bythe wireless communication apparatus STA0 itself, at a timing indicatedby an arrow mark ST11 by advanced space reuse, namely, at a timing aftertransmission of an ACK (Acknowledgement) frame corresponding to thetransmission frame FL11 to the wireless communication apparatus STA1completed. In other words, even if transmission of a signal in theneighboring OBSS 3 was being performed after transmission of a signal inthe BSS 1 of the wireless communication apparatus STA0 itself came to anend, the wireless communication apparatus STA0 could have performedtransmission of the transmission frame FL13 even during transmission ofthe signal in the OBSS 3.

However, since actually the wireless communication apparatus STA0 hasfailed to specify that the transmission frame FL12 has been transmittedfrom a wireless communication apparatus in the OBSS, while thetransmission of the transmission frame FL12 continues, the transmissionframe FL13 cannot be transmitted. Consequently, the transmission frameFL13 comes to be transmitted at a timing indicated by the arrow markST12 after the transmission of the transmission frame FL12 comes to anend, and loss of a transmission opportunity occurs with the wirelesscommunication apparatus STA0.

On the other hand, it is assumed that, for example, the wirelesscommunication apparatus STA1 depicted in FIG. 1 and the wirelesscommunication apparatus STA3 depicted in FIG. 3 perform transmission ofa transmission frame of the configuration depicted in FIGS. 10 and 11and the wireless communication apparatus STA0 performs carrier detectionas depicted in FIG. 17.

In the example depicted in FIG. 17, the wireless communication apparatusSTA1 transmits a transmission frame FL21 and the wireless communicationapparatus STA3 transmits a transmission frame FL22.

Also in this example, similarly as in the example depicted in FIG. 16,at a certain point of time, a state is exhibited in which not onlytransmission of the transmission frame FL21 but also transmission of thetransmission frame FL22 are being performed. Especially, in thisexample, a portion indicated by character “M” inserted in the middle ofthe transmission frame FL21 and the transmission frame FL22 represents amidamble, and HE MID depicted in FIG. 15 is placed in the midamble.

It is assumed that, if, in such a state as described above, the wirelesscommunication apparatus STA0 performs carrier detection in the middle ofthe frames, then the transmission frame FL21 is detected in the middleof transmission and also the transmission frame FL22 is detected in themiddle of transmission.

In this case, although the wireless communication apparatus STA0 hasfailed to decode the top portion of the transmission frame FL21, namely,the preamble portion, since the wireless communication apparatus STA0has successfully decoded the portion of the midamble MD11 in the middleof the frame, the wireless communication apparatus STA0 can acquire BSSColor information from the midamble MD11. Consequently, the wirelesscommunication apparatus STA0 can specify that the transmission frameFL21 is a signal of the BSS 1 of the wireless communication apparatusSTA0 itself. Especially in this example, the wireless communicationapparatus STA0 can acquire BSS Color information from HE MID in themidamble MD11.

Similarly, although the wireless communication apparatus STA0 has failedto decode the preamble part of the transmission frame FL22, since thewireless communication apparatus STA0 has successfully decoded theportion of the midamble MD12 in the middle of the frame, it can acquireBSS Color information from the midamble MD12. Consequently, the wirelesscommunication apparatus STA0 can specify that the transmission frameFL22 is a signal of the OBSS 3 neighboring with the BSS 1 of thewireless communication apparatus STA0 itself.

Accordingly, it becomes possible for the wireless communicationapparatus STA0 to perform signal transmission by advanced space reuse,and the wireless communication apparatus STA0 can perform transmissionof a transmission frame FL23, which is to be transmitted from thewireless communication apparatus STA0 itself, at a timing indicated byan arrow mark ST21 after transmission of an ACK frame corresponding tothe transmission frame FL21 is completed. In other words, even if asignal of an OBSS is detected, the wireless communication apparatus canstart communication in the BSS 1 of the wireless communication apparatusitself and transmit the transmission frame FL23 without waiting for anend of the transmission of the signal of the OBSS.

Here, after the signal in the BSS 1 of the wireless communicationapparatus STA0 itself becomes no more detected, transmission of thetransmission frame FL23 is started within a period within which only thesignal of the OBSS 3 is detected. By the foregoing, in the presenttechnology, it is possible to achieve increase of a transmissionopportunity and perform communication with a high degree of efficiency.

Further, it is assumed that, for example, the access point AP1 depictedin FIG. 1 transmits a transmission frame to the wireless communicationapparatus STA0 and simultaneously the access point AP2 depicted in FIG.1 transmits a transmission frame to the wireless communication apparatusSTA2.

Here, it is assumed that the transmission frames transmitted by theaccess point AP1 and the access point AP2 are frames of a generalconfiguration and are configured such that a midamble including part ofheader information is not inserted therein.

In such a case, for example, if the header information of thetransmission frame cannot be received correctly as depicted in FIG. 18,then the transmission efficiency (communication efficiency) isdeteriorated by re-transmission of the transmission frame.

In the example depicted in FIG. 18, in the middle while the access pointAP1 of the BSS 1 of the wireless communication apparatus STA0 itself istransmitting a transmission frame FL31 destined for the wirelesscommunication apparatus STA0, the access point AP2 of the OBSS 2transmits a transmission frame FL32 destined for the wirelesscommunication apparatus STA2.

Here, since the wireless communication apparatus STA0 has successfullyreceived the transmission frame FL31 correctly, the wirelesscommunication apparatus STA0 transmits an ACK frame FL33 representingsuch reception to the access point AP1.

However, interference (collision) is caused by the ACK frame FL33, andthe wireless communication apparatus STA2 cannot receive thetransmission frame FL32 correctly and is in a state in which acommunication error occurs. The wireless communication apparatus STA2transmits an ACK frame FL34 indicative only of correctly received MPDUsof the transmission frame FL32 to the access point AP2.

Further, although, at the timing of the transmission of the ACK frameFL34, a transmission frame FL35 destined for the wireless communicationapparatus STA0 is transmitted from the access point AP1, a communicationerrors occurs in the wireless communication apparatus STA0 due tointerference between the transmission frame FL35 and the ACK frame FL34.In other words, the wireless communication apparatus STA0 is in a statein which it has failed to correctly receive the transmission frame FL35.The wireless communication apparatus STA0 transmits an ACK frame FL36indicative only of correctly received MPDUs of the transmission frameFL35 to the access point AP1.

Furthermore, although the access point AP2 re-transmits a transmissionframe FL37 corresponding to an MPDU of the transmission frame FL32,which has not been received correctly, in response to the ACK frameFL34, a communication error occurs in the wireless communicationapparatus STA2 due to interference between the transmission frame FL37and the ACK frame FL36. In short, the wireless communication apparatusSTA2 is in a state in which it cannot receive the transmission frameFL37 correctly.

In such a manner, in the example depicted in FIG. 18, duringcommunication from the access point AP1 of the BSS 1 to the wirelesscommunication apparatus STA0, also communication from the access pointAP2 of the neighboring OBSS 2 to the wireless communication apparatusSTA2 is being performed. Then, although communication errors are causedby the ACK frames of the communications, since control of transmissionpower is not performed upon later re-transmission of transmissionframes, collision of signals occurs repeatedly, resulting indeterioration of the communication efficiency.

In the case of a transmission frame of a general configuration, BSSColor information for identify the BSS, transmission power control levelinformation (TPC Level), and parameters (Spatial Reuse) to be applied tothe advanced space reuse technology cannot be obtained in the middle ofa transmission frame. Therefore, in the case where collision of signalsoccurs, control of transmission power cannot be performed uponre-transmission or upon returning of an ACK frame, which sometimescauses repetitive collision of signals.

On the other hand, it is assumed that, for example, the access point AP1depicted in FIG. 1 transmits a transmission frame to the wirelesscommunication apparatus STA0 and simultaneously the access point AP2depicted in FIG. 1 transmits a transmission frame to the wirelesscommunication apparatus STA2 and the transmission frames are frames ofthe configuration depicted in FIG. 10 or 11. In other words, it isassumed that a midamble is deployed in the middle of the transmissionframes as depicted in FIG. 10 or 11 and HE MID depicted in FIG. 15 isplaced in the midamble.

If, in such a state as described above, transmission power control of atransmission frame is performed using information obtained from themidamble, for example, as depicted in FIG. 19 and a signal istransmitted by advanced space reuse, then it is possible to suppressoccurrence of collision of signals and perform communication with ahigher efficiency.

In the example depicted in FIG. 19, in the middle while the access pointAP1 of the BSS 1 of the wireless communication apparatus STA0 itselftransmits a transmission frame FL41 destined for the wirelesscommunication apparatus STA0, the access point AP2 of the OBSS 2transmits a transmission frame FL42 destined for the wirelesscommunication apparatus STA2.

Here, since the wireless communication apparatus STA0 was able tocorrectly receive the transmission frame FL41, the wirelesscommunication apparatus STA0 transmits an ACK frame FL43 representingsuch reception to the access point AP1. Further, at this time, thewireless communication apparatus STA0 has successfully received also amidamble MD21 of the transmission frame FL42.

However, interference (collision) is caused by the ACK frame FL43, andthe wireless communication apparatus STA2 cannot receive thetransmission frame FL42 correctly and is in a state in which acommunication error occurs. The wireless communication apparatus STA2transmits an ACK frame FL44 indicative only of correctly received MPDUsof the transmission frame LF42 to the access point AP2.

Further, although, at the timing of the transmission of the ACK frameFL44, a transmission frame FL45 destined for the wireless communicationapparatus STA0 is transmitted from the access point AP1, a communicationerror occurs in the wireless communication apparatus STA0 due tointerference (collision) of the transmission frame FL45 and the ACKframe FL44.

Furthermore, the access point AP2 re-transmits a transmission frame FL46corresponding to the transmission frame FL42 in response to the ACKframe FL44, and the transmission frame FL46 is received correctly by thewireless communication apparatus STA2. Further, a preamble PR11 of thetransmission frame FL46 is received also by the wireless communicationapparatus STA0.

Since the wireless communication apparatus STA0 has failed to correctlyreceive the transmission frame FL45, the wireless communicationapparatus STA0 transmits an ACK frame FL47 that indicates only MPDUs ofthe transmission frame FL45 received correctly to the access point AP1,and at this time, the wireless communication apparatus STA0 performstransmission power control of the ACK frame FL47.

In particular, the wireless communication apparatus STA0 can acquire BSSColor information, transmission power control level information and soforth on the basis of the midamble MD21 or the preamble PR11 received(detected) in advance. For example, the wireless communication apparatusSTA0 can grasp from the BSS Color information that a signal of the OBSS2 neighboring with the BSS 1 of the wireless communication apparatusSTA0 itself is received.

Therefore, the wireless communication apparatus STA0 transmits the ACKframe FL47 with transmission power of such a level that no collisionoccurs with the transmission frame FL46 on the basis of reception powerof the actually received transmission frame FL46 of the OBSS 2 and soforth. In short, the transmission power for the ACK frame FL47 is setsuch that the ACK frame FL47 may not have an influence on communicationin the OBSS 2.

Consequently, communication that avoids collision of the transmissionframe FL46 and the ACK frame FL47 with each other transmitted atsubstantially same timings can be implemented, and the communicationefficiency can be improved.

Further, even at the access point AP1, access point AP2, and wirelesscommunication apparatus STA2, since, by performing transmission powercontrol similar to that in the case of the wireless communicationapparatus STA0, signals of them do not interfere with each other later,the number of times of re-transmission can be minimized. In other words,coexistence of both communication in the BSS 1 and communication in theOBSS 2 can be achieved and the advanced space reuse technology can becarried out efficiently.

Further, the detection threshold value for detecting a signal from anOBSS and the permissible transmission power of the wirelesscommunication apparatus itself have, for example, such a relationship asdepicted in FIG. 20. It is to be noted that, in FIG. 20, the axis ofabscissa indicates the transmission power of a transmission frametransmitted from the wireless communication apparatus itself, and theaxis of ordinate indicates the reception power (reception electric fieldstrength) of a received signal from an OBSS.

In the example depicted in FIG. 20, a value OBSS_PD_(max) of thereception power is used as the detection threshold value. Further, aregion R11 indicated by slanting lines indicates a range of transmissionpower with which, in the case where the advanced space reuse technologyis applied, when a signal level (reception power) from an OBSS existingin the neighborhood is detected, it is permitted to transmit atransmission frame by transmission power restriction in the BSS of thewireless communication apparatus itself.

In particular, if the transmission power is controlled such that theposition that depends upon the combination of the transmission power ofa transmission frame of the wireless communication apparatus itself andthe reception power of a received signal of an OBSS becomes a positionin the region R11, then the transmission frame can be transmittedwithout having an influence on the communication in the OBSS.

Here, that an influence is not had on communication in an OBSS signifiesa state in which, in the OBSS, collision between a signal of the OBSSand a signal of the BSS does not occur and the signal of the OBSS can bereceived correctly by a wireless communication apparatus of thedestination of the signal.

In other words, even if a signal from an OBSS is detected, if thetransmission power of a transmission frame is determined as transmissionpower equal to or lower than power determined for the reception power ofa signal from the OBSS, then it is possible to transmit the transmissionframe applying the advanced space reuse technology in the BSS of thewireless communication apparatus itself. This can improve thetransmission efficiency.

As described above, in the present technology, a midamble that includespart of header information such as a midamble of the configurationdepicted in FIG. 10 or 11 is deployed in the middle of a transmissionframe, and the midamble is detected by the reception side of thetransmission frame.

Consequently, on the reception side, by detecting the midamble,information (parameters) of part of the header information can beobtained not only from the preamble but also from the midamble, and acharacteristic of the transmission frame can be grasped to performcommunication with a higher efficiency.

In particular, by placing information of part of header information,which cannot be obtained from a transmission frame of a generalconfiguration if the preamble part at the top of the transmission framecannot be decoded correctly, also into a midamble, information of partof the header information can be obtained also from the middle of thetransmission frame. Consequently, advanced space reuse can be carriedout efficiently.

Further, by placing parameters, which are utilized in the advanced spacereuse technology, into the midamble, the reception side of thetransmission frame can decide in the middle of the transmission framewhether or not advanced space reuse is possible.

In particular, by placing, for example, BSS Color information and soforth as parameters to be utilized in the advanced space reusetechnology into the midamble, the wireless communication apparatus canspecify whether the reception frame is a signal of the BSS of thewireless communication apparatus itself or a signal of a different OBSS.

Further, in the present technology, it is made possible to specify, bydetecting a midamble from presence or absence of a specific trainingsequence pattern, whether parameters to be utilized in the advancedspace reuse technology are placed in the midamble. This makes itpossible to specify, in the case where a pattern other than trainingsequence patterns that are utilized in the BSS of the wirelesscommunication apparatus itself is detected, that the received signal isa signal from an overlapping OBSS.

Further, by deploying such information (midamble) at part of asubcarrier, while most part of the subcarrier is utilized fortransmission, parameters to be utilized in the advanced space reusetechnology during data transmission can be notified together.

Furthermore, in the present technology, in addition to the advancedspace reuse technology, Duration information indicative of a duration ofa transmission frame, MCS parameters indicative of a modulation methodand an encoding scheme and so forth can be notified in a form placed inthe midamble.

Further, by deploying a midamble in a unit of an MPDU, a transmissionframe can be decoded for each MPDU, and there is no necessity to performaddition or removal of useless padding.

<Description of Transmission Process>

Now, operation of the wireless communication apparatus 11 is described.

First, a transmission process performed when the wireless communicationapparatus 11 is to transmit a transmission frame is described. Inparticular, a transmission process by the wireless communicationapparatus 11 is described with reference to a flow chart of FIG. 21.

At step S11, the network management section 53 decides whether or nottransmission data is supplied thereto.

For example, in the case where the wireless communication apparatus 11is to transmit transmission data to a different wireless communicationapparatus, transmission data inputted by an application program or thelike is transmitted from the apparatus controlling section 23 to thetransmission buffer 52 through the interface 51 of the wirelesscommunication module 25.

Further, simultaneously when transmission data is supplied to thetransmission buffer 52, destination information indicative of adestination of transmission data, communication partner informationregarding a communication partner of the wireless communicationapparatus 11, and data format information indicative of a data format oftransmission data are supplied from the apparatus controlling section 23to the network management section 53 through the interface 51.

In the case where the destination information, communication partnerinformation, and data format information are supplied from the apparatuscontrolling section 23, the network management section 53 decides atstep S11 that transmission data is supplied thereto.

It is to be noted that the communication partner information isinformation regarding a wireless communication apparatus that becomes adestination of transmission data, and it can be specified, for example,from the communication destination information, a transmission frame ofwhat configuration such as a transmission frame of the configurationdepicted in FIG. 10 or FIG. 11 or the like can be processed by thewireless communication apparatus that becomes a communication partner.

The network management section 53 supplies the destination information,communication partner information, and data format information obtainedin such a manner to the transmission frame construction section 54 andthe wireless communication controlling section 55 as occasion demands.Further, the wireless communication controlling section 55 supplies thedestination information, communication partner information, and dataformat information supplied from the network management section 53 tothe header information generation section 56, midamble generationsection 57 and so forth as occasion demands.

The transmission frame construction section 54 constructs (generates)data of a unit of an MPDU (hereinafter referred to as MPDU data)retained in the transmission buffer 52 using the information suppliedfrom the network management section 53 as occasion demands and suppliesthe data to the wireless transmission processing section 59. Inparticular, the transmission data is placed into and supplied togetherwith an MPDU to the wireless transmission processing section 59.

At this time, for example, the transmission frame construction section54 generates MAC header information at the top of MPDU data on the basisof the destination information and the data format information suppliedfrom the network management section 53. In particular, addressinformation to be included into MAC header information is generated, forexample, on the basis of the destination information.

Such MPDU data corresponds, for example, to the MPDUs indicated bycharacters “MPDU-1” to “MPDU-4” depicted in FIGS. 10 and 11.

It is to be noted that, in the case where the transmission frame has theconfiguration depicted in FIG. 11, the transmission frame constructionsection 54 generates and transmits not only MPDU data but also delimiterinformation to the wireless transmission processing section 59.

In the case where it is decided at step S11 that transmission data isnot supplied, the processing returns to step S11, and the processdescribed above is performed repetitively until transmission data issupplied.

On the other hand, in the case where it is decided at step S11 thattransmission data is supplied, at step S12, the header informationgeneration section 56 performs setting of parameters of headerinformation on the basis of the information supplied from the wirelesscommunication controlling section 55 and so forth.

In particular, the header information generation section 56 generatesL-SIG of the configuration, for example, depicted in FIG. 5 and copies(duplicates) L-SIG to produce RL-SIG, and further generates HE-SIG-A ofthe configuration, for example, depicted in FIG. 6 and lines up L-SIG,RL-SIG, and HE-SIG-A to form header information. After the headerinformation is generated in such a manner, the header informationgeneration section 56 further generates a preamble from the obtainedheader information and L-STF, L-LTF, HE-STF, and HE-LTF and supplies theobtained preamble to the wireless transmission processing section 59.Further, the header information generation section 56 supplies thepreamble including the header information to the midamble generationsection 57.

At step S13, the network management section 53 decides on the basis ofthe communication partner information supplied from the apparatuscontrolling section 23 whether or not a wireless communication apparatusthat becomes a communication partner, namely, a wireless communicationapparatus that becomes a destination (transmission destination) of atransmission frame is ready for a transmission frame of the format(configuration) depicted in FIG. 10 or 11. In short, it is decidedwhether or not the communication partner is ready for reception of atransmission frame of the signal format having a midamble depicted inFIG. 10 or 11.

In the case where it is decided at step S13 that the communicationpartner is ready for such reception as described above, the networkmanagement section 53 instructs the wireless communication controllingsection 55 to generate a midamble depicted in FIG. 10 or 11, andthereafter, the processing advances to step S14.

At step S14, the wireless communication controlling section 55 sets aninsertion position of a midamble in response to the instruction from thenetwork management section 53. For example, the wireless communicationcontrolling section 55 determines a position according the configuration(format) of the transmission frame as the insertion position of amidamble on the basis of the data format information supplied from thenetwork management section 53.

In particular, in the case where the configuration of a transmissionframe indicated by the data format information is, for example, aconfiguration that an MPDU has a fixed length, the wirelesscommunication controlling section 55 determines an insertion positionfor each midamble on the basis of the length (information length) of thepreamble and the length (information length) of an MPDU having the fixedlength. At this time, a midamble is deployed at a position of an OFDMsymbol immediately after each MPDU.

On the other hand, in the case where the configuration of a transmissionframe indicated by the data format information is, for example, aconfiguration that an MPDU has a variable length, the wirelesscommunication controlling section 55 determines an insertion positionfor each midamble on the basis of the information length of the preambleand the information length of each MPDU indicated by the data formatinformation. Also in this case, a midamble is deployed at the positionof an OFDM symbol immediately after each MPDU.

Further, the wireless communication controlling section 55 suppliesinformation necessary for generation of a midamble, for example, theDuration information, transmission power control level information,HE-LTF number information and so forth, to the midamble generationsection 57 and instructs the midamble generation section 57 to generatea midamble.

At step S15, the midamble generation section 57 sets parameters in amidamble on the basis of the information supplied from the wirelesscommunication controlling section 55 and the preamble supplied from theheader information generation section 56. In short, the midamblegeneration section 57 generates a midamble, for example, of theconfiguration depicted in FIGS. 10 and 11.

For example, when a midamble of the configuration depicted in FIG. 10 or11 is to be generated, a midamble including L-STF, L-LTF, L-SIG, HE MID,HE-STF, and a predetermined number of HE-LTF is generated.

Further, the wireless communication controlling section 55 instructs themidamble generation section 57 to output a midamble in response to theinsertion position set at step S14. The midamble generation section 57successively supplies the generated midambles at appropriate timings tothe wireless transmission processing section 59 in accordance with theinstruction of the wireless communication controlling section 55.

By generating a midamble including part of header information such asparameters to be used in the advanced space reuse technology, namely,BSS Color information and so forth in such a manner, it is possible tonotify an ambient wireless communication apparatus, which receives atransmission frame beginning with the middle of the transmission frame,of a characteristic of the transmission frame. This makes it possiblefor the reception side to perform decoding of the transmission framealso beginning with the middle of the transmission frame.

It is to be noted that a plurality of midambles having configurationsdifferent from each other including not only midambles of theconfiguration depicted in FIG. 10 or 11 but also midambles of theconfiguration depicted in any of FIGS. 12 to 14 is prepared in advancesuch that the midamble generation section 57 generates a midamble of anarbitrary configuration from among the plurality of configurations. Insuch a case, the midamble generation section 57 selects oneconfiguration from among the plurality of configurations under thecontrol of the wireless communication controlling section 55 andgenerates midambles of the selected configuration. For example, it issufficient if selection of a configuration for a midamble is performedon the basis of communication partner information or data formatinformation.

After midambles are generated, the processing advances to step S16.

On the other hand, in the case where it is decided at step S13 that thecommunication partner is not ready, the processing thereafter advancesto step S16.

If it is decided at step S13 that the communication partner is not readyor after the process at step S15 is performed, a process at step S16 isperformed.

At step S16, the transmission power controlling section 58 estimates thetransmission power value of the transmission frame to be transmittedfrom the wireless communication apparatus 11 under the control of thewireless communication controlling section 55 and sets the transmissionpower (transmission power) obtained by the estimation. It is to be notedthat the transmission power is set to a value with which thetransmission frame can be received not only by a wireless communicationapparatus that is ready for reception of a transmission frame of theconfiguration depicted in FIG. 10 or 11 but also by a wirelesscommunication apparatus that is not ready for such reception.

In particular, the transmission power controlling section 58 maydetermine transmission power designated by the wireless communicationcontrolling section 55, for example, transmission power indicated bytransmission power controlling level information placed in a midamble,as the transmission power for the transmission power.

Further, the transmission power controlling section 58 may determine thetransmission power for a transmission frame on the basis of thereception power of a signal (reception frame) supplied from the wirelessreception processing section 62 through the detection threshold valuecontrolling section 63 and received by the wireless communicationapparatus 11, namely, on the basis of reception power indicated by areception electric field strength information obtained, for example, atstep S61 of FIG. 22 hereinafter described.

Furthermore, the transmission power controlling section 58 may determinetransmission power for the transmission frame on the basis of both thetransmission power designated by the wireless communication controllingsection 55 and the reception power indicated by the reception electricfield strength information.

In particular, it is sufficient if, whichever method is used todetermine transmission power, the transmission power is determined suchthat the relationship between the reception power and the transmissionpower has a relationship of a position within the region R11 that is apermissible range depicted in FIG. 20 and a wireless communicationapparatus that is to receive the transmission frame can receive thetransmission frame. In other words, it is sufficient if the transmissionpower is determined such that it has a value equal to or lower than apredetermined value that is determined by the reception power, namely,equal to or lower than a predetermined value that is determined by theregion R11 depicted in FIG. 20.

At step S17, the wireless communication controlling section 55 acquiresNAV (Network Allocation Vector) information indicative of a transmissioninhibition period to the BSS of the wireless communication apparatusitself, namely, a period within which transmission of a transmissionframe cannot be performed.

In particular, in the case where the wireless communication apparatus 11receives a transmission frame transmitted from a different wirelesscommunication apparatus as the reception frame, it can acquire BSS Colorinformation placed in the preamble or a midamble of the perceptionframe. In other words, the wireless communication controlling section 55can specify whether the reception frame is a signal of the BSS or asignal of an OBSS from the BSS Color information placed in the headerinformation supplied from the header information analysis section 65 orthe BSS Color information placed in HE MID supplied from the midambledetection section 64.

Then, when the reception frame is a signal of the BSS, the wirelesscommunication controlling section 55 can specify a timing at whichtransmission of MPDU data, namely, of a reception frame, is completedfrom the Duration information placed in the MAC header information ofthe MPDU data extracted from the reception frame and supplied from thereception data construction section 66 through the network managementsection 53.

The wireless communication controlling section 55 generates, on thebasis of a result of the specification of the timing at whichtransmission of the reception frame is completed, NAV informationindicative of a period of time from a current point of time until itbecomes possible for the wireless communication controlling section 55itself to start transmission of the transmission frame after the timingas NAV information for the BSS of the wireless communication apparatusitself. Such NAV information can be considered information indicative ofa communication situation in the BSS.

It is to be noted that the NAV information may be re-set every time MPDUdata is received newly. Further, for generation of NAV information,Duration information in HE MID extracted from a reception frame andsupplied from the midamble detection section 64, length information inthe header information extracted from the reception frame and suppliedfrom the header information analysis section 65 or the like may be used.

Here, every time a predetermined period of time elapses, the value ofthe NAV information of the BSS is decremented by one, and when the valueof the NAV information becomes zero, it becomes possible to transmit thetransmission frame of the wireless communication apparatus itself.

At step S18, the wireless communication controlling section 55 decideswhether or not the transmission frame is to be transmitted by advancedspace reuse.

In the case where it is decided at step S18 that the transmission frameis to be transmitted by advanced space reuse, the wireless communicationcontrolling section 55 acquires the NAV information of an OBSS at stepS19.

In particular, the wireless communication controlling section 55generates NAV information of the OBSS from Duration information, Lengthinformation and so forth obtained from the preamble or a midamble of thereception frame that is decided as a signal of the OBSS similarly asupon acquisition of NAV information of the BSS at step S17. After theNAV information of the OBSS is obtained, the processing advances to stepS20.

In such a manner, by acquiring BSS Color information from a receptionframe or obtaining NAV information of the BSS or an OBSS, the wirelesscommunication apparatus 11 can specify from which one of the BSS and anOBSS the reception frame is originated and can efficiently performcommunication by advanced space reuse.

In the present technology, since BSS Color information for specifyingthe BSS or an OBSS is placed not only in the preamble but also in amidamble, even when reception is performed beginning with the middle ofa reception frame, it can be specified whether the reception frame is asignal of the BSS or a signal of an OBSS.

Therefore, the wireless communication controlling section 55 can obtainNAV information indicative of a communication situation for eachwireless network in regard to the BSS or each OBSS. In other words, thewireless communication controlling section 55 can manage, for eachwireless network, the communication situation of the wireless networkindividually using the NAV information, namely, on the basis of BSSColor information or Duration information.

On the other hand, in the case where it is decided at step S18 that thetransmission frame is not to be transmitted by advanced space reuse, theprocessing thereafter advances to step S20.

In the case where it is decided at step S18 that the transmission frameis not to be transmitted by advanced space reuse, or after the processat step S19 is performed, a process at step S20 is performed.

In particular, at step S20, the wireless communication controllingsection 55 decides on the basis of the NAV information whether or notthe transmission right for the transmission frame is acquired.

For example, in the case where the transmission frame is to betransmitted by advanced space reuse, even if the value of the NAVinformation of an OBSS is not zero, if the value of the NAV informationof the BSS is zero and besides the transmission frame can be transmittedwithout having an influence on a neighboring OBSS from the transmissionpower and the reception power determined at step S16, the wirelesscommunication controlling section 55 decides that the transmission rightis acquired.

In particular, it is assumed that, for example, the reception framebeing received by the wireless communication apparatus 11 is a signal ofan OBSS and its reception power is equal to or lower than predeterminedpower that depends upon the transmission power and the reception powerdepicted in FIG. 20. In this case, the wireless communicationcontrolling section 55 decides that the transmission right of thetransmission frame is acquired, and controls transmission of thetransmission frame by the wireless transmission processing section 59such that the transmission frame is transmitted with the transmissionpower determined by the transmission power controlling section 58 atstep S16.

Further, in the case where the transmission frame is to be transmitted,for example, without performing advanced space reuse, the wirelesscommunication controlling section 55 decides that the transmission rightis acquired when the value of the NAV information of the BSS is zero.

In the case where it is decided at step S20 that the transmission rightis not acquired, the wireless communication controlling section 55increments the value of the NAV information of the BSS and the value ofthe NAV information of the OBSS retained therein individually by oneafter lapse of a predetermined period of time, and thereafter, theprocessing returns to step S20. In short, the process at step S20 isperformed repetitively until the transmission right is acquired.

On the other hand, in the case where it is decided at step S20 that thetransmission right is acquired, the wireless transmission processingsection 59 transmits the preamble of the transmission frame at step S21.

In particular, the wireless transmission processing section 59 performsa conversion process into a baseband signal, a modulation process and soforth for the preamble supplied from the header information generationsection 56 and supplies a transmission signal obtained as a result ofthe processes to the antenna controlling section 60.

Further, the antenna controlling section 60 controls such that thetransmission signal supplied from the wireless transmission processingsection 59 is outputted from the antenna 61. At this time, the wirelesstransmission processing section 59 and the antenna controlling section60 operate such that the transmission signal, namely, the preamble ofthe transmission frame, is transmitted with the transmission power setat step S16 under the control of the transmission power controllingsection 58.

By the process at step S21, from within the transmission frame, the PLCP(Physical Layer Convergence Procedure) header at the top portion of thetransmission frame, namely, the preamble part in which the headerinformation configured from L-SIG, RL-SIG, and HE-SIG-A is included, istransmitted.

At step S22, the wireless transmission processing section 59 transmitsMPDU data of the transmission frame.

In particular, the wireless transmission processing section 59 performsa conversion process into a baseband signal, a modulation process and soforth for the MPDU data supplied from the transmission frameconstruction section 54 and supplies a transmission signal obtained as aresult of the processes to the antenna controlling section 60.

Further, the antenna controlling section 60 controls such that thetransmission signal supplied from the wireless transmission processingsection 59 is outputted from the antenna 61. At this time, the wirelesstransmission processing section 59 and the antenna controlling section60 operate such that the transmission signal, namely, the MPDU data ofthe transmission frame, is transmitted with the transmission power setat step S16 under the control of the transmission power controllingsection 58.

For example, in the case where the transmission frame depicted in FIG.10 is to be transmitted, when the process at step S22 is performedimmediately after the preamble is transmitted, the MPDU data deployedimmediately after the preamble and indicated by character “MPDU-1” istransmitted.

It is to be noted that, in the case also where delimiter information isto be transmitted together with the MPDU data, after the delimiterinformation is transmitted, the MPDU data deployed immediately after thedelimiter information is transmitted.

At step S23, the wireless communication controlling section 55 decideson the basis of a result of setting of the insertion position for amidamble determined by the process at step S14 whether or not a timingat which the midamble is to be outputted comes.

In the case where it is decided at step S23 that the timing at which themidamble is to be outputted comes, the wireless communicationcontrolling section 55 instructs the midamble generation section 57 totransmit the midamble, and thereafter, the processing advances to stepS24.

At step S24, the wireless transmission processing section 59 transmitsthe midamble of the transmission frame.

In particular, the midamble generation section 57 supplies the midambleto be transmitted in accordance with the instruction of the wirelesscommunication controlling section 55 to the wireless transmissionprocessing section 59.

The wireless transmission processing section 59 performs a conversionprocess into a baseband signal, a modulation process and so forth forthe midamble supplied from the midamble generation section 57 andsupplies a transmission signal obtained as a result of the processes tothe antenna controlling section 60.

Further, the antenna controlling section 60 controls such that thetransmission signal supplied from the wireless transmission processingsection 59 is outputted from the antenna 61. At this time, the wirelesstransmission processing section 59 and the antenna controlling section60 operate such that the transmission signal, namely, the midamble ofthe transmission frame, is transmitted with the transmission power setat step S16 under the control of the transmission power controllingsection 58.

After the midamble is transmitted in such a manner, the processingthereafter returns to step S22 and the processes described above arerepeated.

On the other hand, in the case where it is decided at step S23 that thetiming at which a midamble is to be transmitted does not come as yet,the wireless communication controlling section 55 decides at step S25whether or not the tail end of A-MPDU is reached, namely, whether or notthe tail end of the transmission frame is reached.

In the case whether it is decided at step S25 that the tail end is notreached, since transmission of MPDU data or a midamble is to beperformed further, the processing returns to step S22 and the processesdescribed above are performed repetitively.

On the other hand, in the case where it is decided at step S25 that thetail end is reached, the wireless reception processing section 62receives an ACK frame at step S26.

In particular, if the transmission frame transmitted by the wirelesscommunication apparatus 11 is received by a wireless communicationapparatus of the communication partner, then the wireless communicationapparatus of the communication partner transmits an ACK frame destinedfor the wireless communication apparatus 11.

The wireless reception processing section 62 determines that thereception frame supplied from the antenna 61 through the antennacontrolling section 60 is received if the reception power of thereception frame is equal to or higher than the detection threshold valuesupplied from the detection threshold value controlling section 63. Inshort, detection of the preamble and a midamble from the reception frameis performed.

The midamble detection section 64 detects a midamble from the receptionframe by detecting a predetermined sequence pattern at the midamble partfrom the reception frame received by the wireless reception processingsection 62. If a midamble is detected, then the midamble detectionsection 64 supplies L-SIG, HE MID and so forth extracted from themidamble together with a result of the detection to the wirelesscommunication controlling section 55. The midamble detection section 64supplies L-SIG, HE MID and so forth extracted from the midamble also tothe header information analysis section 65 as occasion demands.

The header information analysis section 65 detects the preamble from thereception frame by detecting a predetermined sequence pattern at thepreamble part from the reception frame received by the wirelessreception processing section 62 suitably using the information suppliedfrom the midamble detection section 64 and so forth. If the preamble isdetected, then the header information analysis section 65 suppliesheader information and so forth extracted from the preamble to thewireless communication controlling section 55 together with a result ofthe detection. The header information analysis section 65 supplies theheader information and so froth extracted from the preamble also to thereception data construction section 66.

Further, the reception data construction section 66 extracts thereception data placed in the MPDU data from the reception frame receivedby the wireless reception processing section 62 on the basis of theheader information and so forth supplied from the header informationanalysis section 65, and supplies the reception data to the receptionbuffer 67 and the network management section 53.

In the case where the reception frame received in such a manner is anACK frame, since information indicative of which reception data, namely,which MPDU data, is received correctly, is obtained, the networkmanagement section 53 supplies the information obtained from the ACKframe to the wireless communication controlling section 55.

At step S27, the wireless communication controlling section 55 decideswhether or not an ACK frame indicating that all of the transmission data(MPDU data) of the transmission frame having been transmitted arereceived correctly has been received.

For example, in the case where information indicating that all MPDU dataincluded in the transmission frame transmitted already are receivedcorrectly is received from the network management section 53, thewireless communication controlling section 55 decides that an ACK frameindicating such correct reception is received. With this, thetransmission frame is received correctly by the wireless communicationapparatus of the communication partner.

In the case where it is decided at step S27 that an ACK frame indicatingthat the transmission frame is received correctly is not received, theprocessing returns to step S12 and the processes described above areperformed repeatedly.

In this case, since the transmission frame has not been receivedcorrectly, the transmission frame comes to be re-transmitted. However,in this case, since control of the transmission power is performedappropriately at step S16, communication is performed more efficiently.

On the other hand, in the case where it is decided at step S27 that anACK frame indicating that the transmission frame is received correctlyis received, since the transmission frame has been received correctly bythe communication partner side, the transmission process is ended.

In this manner, the wireless communication apparatus 11 places andtransmits part of header information into and together with a midamble.Consequently, communication can be performed with a higher efficiency.

<Description of Reception Process>

Now, a reception process that is performed when the wirelesscommunication apparatus 11 receives a reception from transmitted from acommunication partner is described. In particular, the reception processby the wireless communication apparatus 11 is described below withreference to a flow chart of FIG. 22.

After a reception process is started, the wireless communicationapparatus 11 first starts operation of the blocks that function as areceiver of the wireless communication apparatus 11 itself in order toreceive a reception frame destined for the wireless communicationapparatus 11 itself.

Then at step S61, the wireless reception processing section 62 detectsreception power, namely, a reception electric field strength, of areception frame supplied from the antenna 61 through the antennacontrolling section 60 and acquires reception electric field strengthinformation indicative of the reception power (signal detection level).

At this time, for example, if the reception power of the reception framedetermined (detected) by the wireless reception processing section 62 isequal to or higher than a detection threshold value supplied from thedetection threshold value controlling section 63, then detection of thepreamble and a midamble of the reception frame is performed. It is to benoted that, more particularly, detection of the preamble and a midambleis performed also from a reception frame whose reception power is lowerthan the detection threshold value.

The midamble detection section 64 detects a midamble from the receptionframe by detecting a predetermined sequence pattern at a midamble partfrom the reception frame received by the wireless reception processingsection 62.

Further, the header information analysis section 65 detects the preamblefrom the reception frame by detecting a predetermined sequence patternat the preamble part from the reception frame received by the wirelessreception processing section 62 suitably using information supplied fromthe midamble detection section 64 and so forth.

It is to be noted that the detection threshold value controlling section63 performs a process for setting a preamble detection threshold valuefor the BSS from a predetermined reception electric field strength leveland determining a detection threshold value according to the slope fromOBSS_PD_(max) to OBSS_PD_(min) in response to the transmission power forthe frame to be transmitted, described hereinabove with reference toFIG. 20 in regard to the preamble detection threshold value for an OBSS.

For example, in the case where preamble detection is decided first fromthe threshold value for the reception power of a reception frame of theBSS supplied from the wireless reception processing section 62 and thenit is decided that the reception signal is a signal from an OBSS, thedetection threshold value controlling section 63 carries out decision ofthe detection threshold value for OBSS_PD in response to thetransmission power for a frame to be transmitted.

Here, the reception power of the reception frame of the BSS or an OBSSsupplied from the wireless reception processing section 62 is receptionpower indicated by the reception electric field strength informationdetermined by the process at step S61. Whether the reception powerindicated by the reception electric field strength information is thatof a signal of the BSS or a signal of an OBSS can be specified from BSSColor information supplied from the wireless communication controllingsection 55.

At step S62, the header information analysis section 65 decides whetheror not the preamble is detected from the reception frame.

In the case where it is decided at step S62 that the preamble isdetected, the processing advances to step S63.

At step S63, the header information analysis section 65 extracts headerinformation and so forth from the detected preamble, supplies the headerinformation and so forth to the wireless communication controllingsection 55 and the reception data construction section 66, and then theprocessing advances to step S66. Consequently, the PLCP header, namely,header information including L-SIG, RL-SIG, and HE-SIG-A, is extractedfrom the preamble of the reception frame.

On the other hand, in the case where it is decided at step S62 that thepreamble is not detected, the midamble detection section 64 decideswhether or not a midamble is detected from the reception frame at stepS64.

In the case where it is decided at step S64 that a midamble is detected,the processing thereafter advances to step S65.

At step S65, the midamble detection section 64 extracts variousparameters from the detected midamble, and the processing thereafteradvances to step S66.

In particular, the midamble detection section 64 extracts variousparameters placed in L-SIG and HE MID from the midamble and supplies theparameters to the wireless communication controlling section 55 and theheader information analysis section 65.

Further, the various parameters placed in L-SIG and HE MID obtained bythe midamble detection section 64 are supplied also to the receptiondata construction section 66 through the header information analysissection 65 as occasion demands. Since BSS Color information and so forthare obtained as parameters placed, for example, in L-SIG and HE MID areobtained, even when a reception frame is detected in the middle of theframe, the midamble detection section 64 can specify whether thereception frame is a signal of the BSS or a signal of an OBSS, andcommunication can be performed with a higher efficiency.

Further, since parameters and so forth relating to the advanced spacereuse technology can be obtained from L-SIG and HE MID of the midamble,even when a reception frame is received beginning with the middle of thereception frame, decoding of the reception frame, namely, extraction ofreception data, can be performed.

Further, if a preamble and a midamble are detected from the receptionframe, then the reception data construction section 66 analyzes MACheader information placed in MPDU data from the reception frame receivedby the wireless reception processing section 62 on the basis of theheader information and so forth supplied from the header informationanalysis section 65. Consequently, it is possible to acquire addressinformation indicated by character “Address” in the MAC headerinformation depicted, for example, in FIG. 7, and the reception dataconstruction section 66 supplies the acquired address information to thewireless communication controlling section 55 through the networkmanagement section 53.

After the process at step S63 or step S65 is performed, the wirelesscommunication controlling section 55 decides at step S66 whether or notthe received reception frame is a signal of the BSS of the wirelesscommunication apparatus 11 itself.

For example, in the case where BSS Color information included inHE-SIG-A in the header information is supplied from the headerinformation analysis section 65, when the BSS Color information isinformation indicative of the BSS to which the wireless communicationapparatus 11 belongs, the wireless communication controlling section 55decides that the reception signal is a signal of the BSS wirelesscommunication apparatus 11 itself.

On the other hand, in the case where BSS Color information included inHE-MID is supplied from the midamble detection section 64, when the BSSColor information is information indicative of the BSS to which thewireless communication apparatus 11 belongs, the wireless communicationcontrolling section 55 decides that the reception signal is a signal ofthe BSS of the wireless communication apparatus 11 itself.

In the case where it is decided at step S66 that the reception signal isa signal of the BSS of the wireless communication apparatus 11 itself,the wireless communication controlling section 55 decides at step S67whether or not the received reception frame is data (reception frame)destined for the wireless communication apparatus 11 itself.

For example, in the case where the address information supplied from thereception data construction section 66 through the network managementsection 53 indicates the wireless communication apparatus itself,namely, the wireless communication apparatus 11 itself, the wirelesscommunication controlling section 55 decides that the reception signalis data destined for the wireless communication apparatus itself.

In the case where it is decided at step S67 that the reception signal isdata destined for the wireless communication apparatus itself, theprocessing advances to step S68.

At step S68, the reception data construction section 66 extracts thereception data placed in one MPDU data from the reception frame receivedby the wireless reception processing section 62 on the basis of theheader information and so forth supplied from the header informationanalysis section 65. In short, extraction of the reception data in aunit of an MPDU is performed.

The reception data construction section 66 supplies the extractedreception data to the network management section 53 and the receptionbuffer 67. The reception data retained in the reception buffer 67 issupplied to the apparatus controlling section 23 through the interface51.

At step S69, the reception data construction section 66 decides whetheror not MPDU data, namely, reception data in a unit of an MPDU, isreceived correctly as a result of step S68.

In the case where it is decided at step S69 that MPDU data issuccessfully received correctly, the reception data construction section66 constructs (generates) ACK information indicating that the MPDU datais received correctly and supplies the ACK information to the wirelesscommunication controlling section 55 through the network managementsection 53 at step S70. After the ACK information is generated, theprocessing advances to step S71.

On the other hand, in the case where it is decided at step S69 that theMPDU data is not received correctly, the process at step S70 is notperformed, and the processing advances to step S71.

If it is decided at step S69 that the MPDU data is not receivedcorrectly or after the process at step S70 is performed, a process atstep S71 is performed.

In particular, at step S71, the wireless communication controllingsection 55 decides whether or not the tail end of aggregate A-MPDU isreached, namely, whether or not the tail end of the reception frame isreached, on the basis of the header information and so forth suppliedfrom the header information analysis section 65 and the midambledetection section 64.

In the case where it is decided at step S71 that the tail end of A-MPDUis not reached as yet, the processing returns to step S68 and theprocesses described above are performed repeatedly.

On the other hand, in the case where it is decided at step S71 that thetail end of A-MPDU is reached, the wireless transmission processingsection 59 transmits the ACK frame at step S72.

In particular, the wireless communication controlling section 55controls the header information generation section 56 on the basis ofthe ACK information supplied from the reception data constructionsection 66 to generate a preamble for the ACK frame and supply thepreamble to the wireless transmission processing section 59. Further,the network management section 53 controls the transmission frameconstruction section 54 on the basis of the ACK information suppliedfrom the reception data construction section 66 to generate MPDU datafor the ACK frame and supply the MPDU data to the wireless transmissionprocessing section 59 as occasion demands.

The wireless transmission processing section 59 performs a conversionprocess into a baseband signal, a modulation process and so forth forthe preamble supplied from the header information generation section 56and the ACK frame configured from the MPDU data supplied from thetransmission frame construction section 54 and supplies an ACK frameobtained as a result of the processes to the antenna controlling section60.

Further, the antenna controlling section 60 controls such that the ACKframe supplied from the wireless transmission processing section 59 isoutputted from the antenna 61. At this time, the wireless transmissionprocessing section 59 and the antenna controlling section 60 operatesuch that the ACK frame is transmitted with the transmission power set,for example, in a similar manner as at step S16 of FIG. 21 under thecontrol of the transmission power controlling section 58.

For example, the ACK frame supplied from the wireless transmissionprocessing section 59 includes information indicative of correctlyreceived MPDU data. After the ACK frame is transmitted in such a manneras described above, the reception process is ended.

On the other hand, in the case where it is decided at step S67 that thereception signal is not data destined for the wireless communicationapparatus itself, namely, in the case where, although the BSS Colorinformation included in the reception frame is information indicative ofthe BSS of the wireless communication apparatus itself, the receptionframe is not destined for the wireless communication apparatus itself,the processing advances to step S73.

At step S73, the wireless communication controlling section 55 sets orupdates NAV information of the BSS of the wireless communicationapparatus itself.

In particular, in the case where the wireless communication controllingsection 55 does not retain NAV information of the BSS of the wirelesscommunication apparatus itself, it generates NAV information of the BSSof the wireless communication apparatus itself in a similar manner as inthe case at step S17 of FIG. 21.

In particular, NAV information of the BSS is generated, for example,from the Duration information placed in the MAC header information ofthe MPDU data supplied from the reception data construction section 66through the network management section 53, Duration information in HEMID supplied from the midamble detection section 64, length informationsupplied from the header information analysis section 65 and so forth.

On the other hand, in the case where the wireless communicationcontrolling section 55 already retains NAV information of the BSS of thewireless communication apparatus itself, the wireless communicationcontrolling section 55 updates the retained NAV information on the basisof the Duration information and so forth placed in the MAC headerinformation of the MPDU data received newly.

In the case where, although the BSS Color information included in thereception frame is information indicative of the BSS of the wirelesscommunication apparatus itself, the reception frame is not destined forthe wireless communication apparatus itself, communication fortransmission and reception of the reception frame continues to beperformed till time indicated by the Duration information placed in theMAC header information.

After the NAV information of the BSS of the wireless communicationapparatus itself is generated or updated in such a manner, theprocessing advances to step S78.

On the other hand, in the case where it is decided at step S66 that thereception signal is not a signal of the BSS of the wirelesscommunication apparatus itself, the wireless communication controllingsection 55 decides at step S74 whether or not the received receptionframe is a signal of an OBSS.

For example, in the case where BSS Color information included inHE-SIG-A in the header information is supplied from the headerinformation analysis section 65, the wireless communication controllingsection 55 decides that the BSS Color information is informationindicative of a different BSS, to which the wireless communicationapparatus 11 does not belong, namely, indicative of an OBSS, thewireless communication controlling section 55 decides that the receptionsignal is a signal of an OBSS.

Further, in the case where BSS Color information included in HE-MID issupplied from the midamble detection section 64, the wirelesscommunication controlling section 55 decides that the reception signalis a signal of an OBSS when the BSS Color information is informationindicative of an OBSS to which the wireless communication apparatus 11does not belong.

In the case where it is decided at step S74 that the reception signal isa signal of an OBSS, the wireless communication controlling section 55sets or updates the NAV information of the OBSS at step S75.

In particular, at step S75, a process similar to that at step S73 isperformed to generate or update NAV information of the OBSS. It is to benoted that the NAV information of the OBSS may be generated for eachOBSS or only NAV information of an OBSS whose duration is longest amonga plurality of OBSSes may be set (generated) and managed.

Similarly as upon transmission processing, also upon receptionprocessing, by managing NAV information for each of a wireless networkin regard to the BSS and each OBSS, the wireless communicationcontrolling section 55 can manage the communication situation of thewireless network individually using the NAV information.

After the NAV information of the OBSS is set or updated, the processingadvances to step S78.

On the other hand, in the case where it is decided at step S74 that thereception signal is not a signal of an OBSS, the processing thereafteradvances to step S77.

On the other hand, in the case where it is decided at step S64 that amidamble is not detected, the processing advances to step S76.

At step S76, the wireless communication controlling section 55 decideswhether or not the reception power of the reception frame received bythe wireless reception processing section 62 is higher than a detectionthreshold value determined by the detection threshold value controllingsection 63.

In the case where it is decided at step S76 that the reception power ofthe reception frame is higher than the detection threshold value, thewireless communication controlling section 55 determines at step S77that it is in a state in which it is detecting a carrier, andthereafter, the processing advances to step S78.

In this case, although none of a preamble and a midamble are detected inregard to the reception frame, since the wireless communicationcontrolling section 55 is in a state in which a signal having highreception power is detected, the wireless communication controllingsection 55 determines that this is a state during carrier detection andcontinuously performs the process for detecting a preamble or a midamblefrom the signal being received (reception frame). It is to be notedthat, in the state in which the carrier is being detected, the wirelesscommunication apparatus 11 cannot perform transmission of a transmissionframe.

On the other hand, in the case where it is decided at step S76 that thereception power is equal to or lower than the detection threshold value,the wireless communication apparatus 11 does not determine that thecarrier is being detected, and the processing thereafter advances tostep S78.

Further, in the case where the process at step S73 is performed, in thecase where the process at step S75 is performed, in the case where theprocess at step S77 is performed or in the case where it is decided atstep S76 that the reception power is equal to or lower than thedetection threshold value, a process at step S78 is performed.

In particular, at step S78, the wireless communication controllingsection 55 acquires all NAV information. In particular, the wirelesscommunication controlling section 55 reads out the NAV information ofthe BSS of the wireless communication apparatus itself obtained at stepS73 and the NAV information of the OBSS obtained at step S75 and graspsthe communication situation of the BSS and the OBSS indicated by the NAVinformation.

At step S79, the wireless communication controlling section 55 decideswhether or not a predetermined period of time elapses after the NAVinformation is updated last.

In the case where it is decided at step S79 that the predeterminedperiod of time does not elapse as yet, the processing returns to stepS61 and the processes described above are performed repeatedly.

On the other hand, in the case where it is decided at step S79 that thepredetermined period of time elapses, the wireless communicationcontrolling section 55 subtracts one from the NAV information of the BSSof the wireless communication apparatus itself and the NAV informationof the OBSS at step S80. In other words, the values of the NAVinformation are decremented.

At step S81, the wireless communication controlling section 55 decideswhether or not the values of all NAV information are zero.

In the case where it is decided at step S81 that the values of all NAVinformation are not zero, the processing returns to step S61 and theprocesses described above are performed repeatedly.

On the other hand, in the case where it is decided at step S81 that thevalues of all NAV information are zero, the reception process is ended.

In such a manner, the wireless communication apparatus 11 detects amidamble in which part of header information is placed from a receptionframe and extracts part of the header information from the midamble.Consequently, communication can be performed with a higher efficiency.

<Configuration Example of Computer>

Incidentally, while the series of processes described above can beexecuted by hardware, it may otherwise be executed by software. In thecase where the series of processes is executed by software, a programthat constructs the software is installed into a computer. Here, as thecomputer, a computer incorporated in hardware for exclusive use, forexample, a personal computer for universal use that can execute variousfunctions by installing various programs, and so forth are available.

FIG. 23 is a block diagram depicting a configuration example of hardwareof a computer that executes the series of processes describedhereinabove in accordance with a program.

In the computer, a CPU 501, a ROM (Read Only Memory) 502, and a RAM(Random Access Memory) 503 are connected to each other by a bus 504.

To the bus 504, an input/output interface 505 is connected further. Tothe input/output interface 505, an inputting section 506, an outputtingsection 507, a recording section 508, a communication section 509, and adrive 510 are connected.

The inputting section 506 is configured from a keyboard, a mouse, amicrophone, an imaging element and so forth. The outputting section 507is configured from a display, a speaker and so forth. The recordingsection 508 is configured from a hard disk, a nonvolatile memory and soforth. The communication section 509 is configured from a networkinterface or the like. The drive 510 drives a removable recording medium511 such as a magnetic disk, an optical disk, a magneto-optical disk, asemiconductor memory or the like.

In the computer configured in such a manner as described above, the CPU501 loads a program recorded, for example, in the recording section 508into the RAM 503 through the input/output interface 505 and the bus 504to perform the series of processes described above.

The program that is executed by the computer (CPU 501) can be recordedinto and provided as the removable recording medium 511, for example, asa package medium or the like. Further, the program can be providedthrough a wired or wireless transmission medium such as a local areanetwork, the Internet, a digital satellite broadcast or the like.

In the computer, a program can be installed into the recording section508 through the input/output interface 505 by mounting a removablerecording medium 511 on the drive 510. Further, the program can bereceived by the communication section 509 through a wired or wirelesstransmission medium and installed into the recording section 508.Further, the program can be installed in advance into the ROM 502 or therecording section 508.

It is to be noted that the program executed by the computer may be aprogram in which processes are performed in time series in accordancewith the order described herein or may be a program in which processesare executed in parallel or at a necessary timing such as, for example,when the program is called or the like.

Further, the embodiment of the present technology is not limited to theembodiment described hereinabove, and various alterations are possiblewithout departing from the subject matter of the present disclosure.

For example, the present technology can assume a configuration for cloudcomputing in which one function is shared and processed cooperatively bya plurality of apparatus through a network.

Further, the steps described hereinabove in connection with the flowcharts can be executed by a single apparatus or can be executed bysharing by a plurality of apparatus.

Furthermore, where one step includes a plurality of processes, theplurality of processes included in the one step can be executed by asingle apparatus and also can be executed by sharing by a plurality ofapparatus.

It is to be noted that the present technology can assume such aconfiguration as described below.

(1)

A wireless communication apparatus, including:

a preamble generation section configured to generate a preamble that isto be deployed at a top of a transmission frame and includes headerinformation;

a midamble generation section configured to generate a midamble that isto be deployed in a middle of the transmission frame and includesinformation of at least part of the header information; and

a wireless transmission processing section configured to transmit thetransmission frame including the preamble and the midamble.

(2)

The wireless communication apparatus according to (1), in which

the midamble includes a field of at least part of fields included in thepreamble other than the header information.

(3)

The wireless communication apparatus according to (2), in which

the fields other than the header information include fields fortraining.

(4)

The wireless communication apparatus according to (2) or (3), in which

the deployment in the midamble and the deployment in the preamble of thefield that is included in common in the midamble and the preamble aresame as each other.

(5)

The wireless communication apparatus according to (2) or (3), in which

the deployment in the midamble and the deployment in the preamble of thefield that is included in common in the midamble and the preamble aredifferent from each other.

(6)

The wireless communication apparatus according to any one of (1) to (4),in which

the midamble generation section generates the midamble of oneconfiguration from among a plurality of the midambles havingconfigurations different from each other.

(7)

The wireless communication apparatus according to any one of (1) to (6),in which

the midamble is deployed at each of intervals of a data unit included inthe transmission frame.

(8)

The wireless communication apparatus according to (7), in which,

in a case where the data unit has a variable length, delimiterinformation indicative of an information length of the data unit isdeployed immediately preceding to the data unit in the transmissionframe.

(9)

The wireless communication apparatus according to any one of (1) to (8),in which

the midamble includes at least any one of information indicative oftransmission power of the transmission frame, information for advancedspace reuse, information for specifying a wireless network to which thewireless communication apparatus belongs, encoding scheme information ofthe transmission frame, or information indicative of a duration of thetransmission frame.

(10)

The wireless communication apparatus according to any one of (1) to (9),further including:

a wireless reception processing section configured to detect receptionpower of a received reception frame; and

a transmission power controlling section configured to controltransmission power of the transmission frame based on the receptionpower.

(11)

The wireless communication apparatus according to (10), in which

the transmission power controlling section controls the transmissionpower of the transmission frame based on information included in themidamble of the transmission frame and indicative of transmission powerof the transmission frame and the reception power.

(12)

The wireless communication apparatus according to (10) or (11), inwhich,

in a case where the reception frame is a signal of a wireless networkdifferent from a wireless network to which the wireless communicationapparatus belongs and the reception power is equal to or lower than agiven value, the wireless transmission processing section transmits thetransmission frame with the transmission power determined by thetransmission power controlling section.

(13)

A wireless communication method, including the steps of:

generating a preamble that is to be deployed at a top of a transmissionframe and includes header information;

generating a midamble that is to be deployed in a middle of thetransmission frame and includes information of at least part of theheader information; and transmitting the transmission frame includingthe preamble and the midamble.

(14)

A program for causing a computer to execute a process including thesteps of:

generating a preamble that is to be deployed at a top of a transmissionframe and includes header information;

generating a midamble that is to be deployed in a middle of thetransmission frame and includes information of at least part of theheader information; and

transmitting the transmission frame including the preamble and themidamble.

(15)

A wireless communication apparatus, including:

a wireless reception processing section configured to receive areception frame that includes a preamble deployed at a top of thereception frame and including header information and a midamble deployedin a middle of the frame and including information of at least part ofthe header information; and

a midamble detection section configured to detect the midamble from thereception frame and extract the information of the at least part of theheader information included in the midamble.

(16)

The wireless communication apparatus according to (15), in which

the midamble includes a field of at least part of fields included in thepreamble other than the header information.

(17)

The wireless communication apparatus according to (16), in which

the fields other than the header information include fields fortraining.

(18)

The wireless communication apparatus according to (16) or (17), in which

the deployment in the midamble and the deployment in the preamble of thefield that is included in common in the midamble and the preamble aresame as each other.

(19)

The wireless communication apparatus according to (16) or (17), in which

the deployment in the midamble and the deployment in the preamble of thefield that is included in common in the midamble and the preamble aredifferent from each other.

(20)

The wireless communication apparatus according to any one of (15) to(19), in which

the midamble is deployed at each of intervals of a data unit included inthe reception frame.

(21)

The wireless communication apparatus according to (20), in which,

in a case where the data unit has a variable length, delimiterinformation indicative of an information length of the data unit isdeployed immediately preceding to the data unit in the reception frame.

(22)

The wireless communication apparatus according to any one of (15) to(21), in which

the midamble includes at least any one of information indicative oftransmission power of the reception frame, information for advancedspace reuse, information for specifying a wireless network to which atransmission source of the reception frame belongs, encoding schemeinformation of the reception frame, or information indicative of aduration of the reception frame.

(23)

The wireless communication apparatus according to any one of (15) to(22), in which

the wireless reception processing section detects reception power of thereception frame, and

the wireless communication apparatus further includes a transmissionpower controlling section configured to control transmission power of atransmission frame to be transmitted later based on the reception power.

(24)

The wireless communication apparatus according to (23), in which

the transmission power controlling section controls the transmissionpower of the transmission frame based on information included in themidamble of the transmission frame and indicative of transmission powerof the transmission frame and the reception power.

(25)

The wireless communication apparatus according to any one of (15) to(24), further including:

a wireless communication controlling section configured to individuallymanage, based on information that specifies a wireless network to whicha transmission source of the reception frame belongs and informationindicative of a duration of the reception frame, both included in themidamble of the reception frame, a communication situation of a wirelessnetwork to which the wireless communication apparatus belongs and acommunication situation of a wireless network different from thewireless network to which the wireless communication apparatus belongs.

(26)

A wireless communication method, including the steps of:

receiving a reception frame that includes a preamble deployed at a topof the reception frame and including header information and a midambledeployed in a middle of the frame and including information of at leastpart of the header information; and detecting the midamble from thereception frame and extracting the information of the at least part ofthe header information included in the midamble.

(27)

A program for causing a computer to execute a process including thesteps of:

receiving a reception frame that includes a preamble deployed at a topof the reception frame and including header information and a midambledeployed in a middle of the frame and including information of at leastpart of the header information; and

detecting the midamble from the reception frame and extracting theinformation of the at least part of the header information included inthe midamble.

(28)

A wireless communication system including a first wireless communicationapparatus configured to transmit a transmission frame and a secondwireless communication apparatus configured to receive the transmissionframe, in which

the first wireless communication apparatus includes

-   -   a preamble generation section configured to generate a preamble        that is to be deployed at a top of the transmission frame and        includes header information,    -   a midamble generation section configured to generate a midamble        that is to be deployed in a middle of the transmission frame and        includes information of at least part of the header information,        and

a wireless transmission processing section configured to transmit thetransmission frame including the preamble and the midamble, and

the second wireless communication apparatus includes

-   -   a wireless reception processing section configured to receive        the transmission frame, and    -   a midamble detection section configured to detect the midamble        from the transmission frame and extract the information of the        at least part of the header information included in the        midamble.

REFERENCE SIGNS LIST

-   -   11 Wireless communication apparatus, 53 Network management        section, 54 Transmission frame construction section, 55 Wireless        communication controlling section, 56 Header information        generation section, 57 Midamble generation section, 58        Transmission power controlling section, 59 Wireless transmission        processing section, 62 Wireless reception processing section, 64        Midamble detection section, 65 Header information analysis        section, 66 Reception data construction section

1. A wireless communication apparatus, comprising: a preamble generationsection configured to generate a preamble that is to be deployed at atop of a transmission frame and includes header information; a midamblegeneration section configured to generate a midamble that is to bedeployed in a middle of the transmission frame and includes informationof at least part of the header information; and a wireless transmissionprocessing section configured to transmit the transmission frameincluding the preamble and the midamble.
 2. The wireless communicationapparatus according to claim 1, wherein the midamble includes a trainingfield of at least part of fields included in the preamble other than theheader information.
 3. The wireless communication apparatus according toclaim 2, wherein the deployment in the midamble and the deployment inthe preamble of the field that is included in common in the midamble andthe preamble are same as each other.
 4. The wireless communicationapparatus according to claim 2, wherein the deployment in the midambleand the deployment in the preamble of the field that is included incommon in the midamble and the preamble are different from each other.5. The wireless communication apparatus according to claim 1, whereinthe midamble is deployed at each of intervals of a data unit included inthe transmission frame.
 6. The wireless communication apparatusaccording to claim 5, wherein, in a case where the data unit has avariable length, delimiter information indicative of an informationlength of the data unit is deployed immediately preceding to the dataunit in the data unit in the transmission.
 7. The wireless communicationapparatus according to claim 1, wherein the midamble includes at leastany one of information indicative of transmission power of thetransmission frame, information for advanced space reuse, informationfor specifying a wireless network to which the wireless communicationapparatus belongs, encoding scheme information of the transmissionframe, or information indicative of a duration of the transmissionframe.
 8. The wireless communication apparatus according to claim 1,further comprising: a wireless reception processing section configuredto detect reception power of a received reception frame; and atransmission power controlling section configured to controltransmission power of the transmission frame based on the receptionpower.
 9. The wireless communication apparatus according to claim 8,wherein, in a case where the reception frame is a signal of a wirelessnetwork different from a wireless network to which the wirelesscommunication apparatus belongs and the reception power is equal to orlower than a given value, the wireless transmission processing sectiontransmits the transmission frame with the transmission power determinedby the transmission power controlling section.
 10. A wirelesscommunication method, comprising the steps of: generating a preamblethat is to be deployed at a top of a transmission frame and includesheader information; generating a midamble that is to be deployed in amiddle of the transmission frame and includes information of at leastpart of the header information; and transmitting the transmission frameincluding the preamble and the midamble.
 11. A wireless communicationapparatus, comprising: a wireless reception processing sectionconfigured to receive a reception frame that includes a preambledeployed at a top of the reception frame and including headerinformation and a midamble deployed in a middle of the frame andincluding information of at least part of the header information; and amidamble detection section configured to detect the midamble from thereception frame and extract the information of the at least part of theheader information included in the midamble.
 12. The wirelesscommunication apparatus according to claim 11, wherein the midambleincludes a training field of at least part of fields included in thepreamble other than the header information.
 13. The wirelesscommunication apparatus according to claim 12, wherein the deployment inthe midamble and the deployment in the preamble of the field that isincluded in common in the midamble and the preamble are same as eachother.
 14. The wireless communication apparatus according to claim 12,wherein the deployment in the midamble and the deployment in thepreamble of the field that is included in common in the midamble and thepreamble are different from each other.
 15. The wireless communicationapparatus according to claim 11, wherein the midamble is deployed ateach of intervals of a data unit included in the reception frame. 16.The wireless communication apparatus according to claim 15, wherein, ina case where the data unit has a variable length, delimiter informationindicative of an information length of the data unit is deployedimmediately preceding to the data unit in the reception frame.
 17. Thewireless communication apparatus according to claim 11, wherein themidamble includes at least any one of information indicative oftransmission power of the reception frame, information for advancedspace reuse, information for specifying a wireless network to which atransmission source of the reception frame belongs, encoding schemeinformation of the reception frame, or information indicative of aduration of the reception frame.
 18. The wireless communicationapparatus according to claim 11, wherein the wireless receptionprocessing section detects reception power of the reception frame, andthe wireless communication apparatus further includes a transmissionpower controlling section configured to control transmission power of atransmission frame to be transmitted later based on the reception power.19. The wireless communication apparatus according to claim 11, furthercomprising: a wireless communication controlling section configured toindividually manage, based on information that specifies a wirelessnetwork to which a transmission source of the reception frame belongsand information indicative of a duration of the reception frame, bothincluded in the midamble of the reception frame, a communicationsituation of a wireless network to which the wireless communicationapparatus belongs and a communication situation of a wireless networkdifferent from the wireless network to which the wireless communicationapparatus belongs.
 20. A wireless communication method, comprising thesteps of: receiving a reception frame that includes a preamble deployedat a top of the reception frame and including header information and amidamble deployed in a middle of the frame and including information ofat least part of the header information; and detecting the midamble fromthe reception frame and extracting the information of the at least partof the header information included in the midamble.